As they are widely spread and I’m not sure whether the people who are interested in them can find them easily, I’d like to make a list of links to every topic regarding handmade cards and mail art.
This is a WIKI! That means that we all can edit this post, add new topics or change broken links etc.
But you can also simply write a post in this topic if you found a topic or a group in an RR or anything else that fits this theme that is still missing–or if a topic is closed that is still listed here–and I am going to add it for you.
If you want to watch or track this topic, you are going to receive a notification of every new addition to this directory.
Link to the original thread in the legacy forum: Postcrossing (Legacy) Forum - DIRECTORY Handmade Cards and Mail Art
Discussions
Feedback Wanted
Can you give me some suggestions on my self designed postcards?
New post card designs. Need your help
Please give your thoughts on my homemade cards
Will the joke/pun be understood outside the US
Would anyone be interested in this?
General
Custom made cards, acceptable?
Deciding on handmade postcard size
Do you like decorated postcards?
Do you make postcards by yourself?
Do your handmade cards also get more often lost on the way?
First attempt at handmade card - help!
Handmade… Is this really a postcard?
How to make a postcard？
“I’m not an artist!” 
(Yes, you are)
Is it considered as a postcard?
Post card artists
Sending A Disliked Card
What classes as a hand made card?
What is “a real postcard”?
What postcrossing gave me and what postcrossers took away from me
Where to buy handmade cards
Why do so many people hate selfmade cards?
Materials
Crafts with old Postage stamps
Custom ink stamps
Do tapes and stickers ruin postcards?
Glue & adhesives for mailart
Handmade Stickers
Laminated cards
Paint color cards
Panel Canvas Postcards
Repurposing greeting cards into postcards?
Sources for personalized stamps
Postcards to colour
Unique material and Unusual Postcard
What are your favorite medium(s) to use when creating your mail art/handmade cards?
What do you coat handmade postcards in to protect the design?
What do you make handmade cards out of?
Yarn on Handmade Cards?
Meeting cards (Discussions)
Designing Postcrossing Meeting Cards
Do people like meetup cards?
Meetup cards are must-have?
Meetups Guidelines: feedback welcome!
Where to get a postcrossing meetup card？
Other
Interesting Needlework Postcard Challenge
Trying to find a user
"What is the craziest design you would like to see on a postcard but you can’t find in any shop”
What type of PostCards interest you more?
Who among you believes in DESTINY?
Postcrossing rules and guidelines
How to make a postcard with “postcrossing” logo?
[QUESTION] The rule of the usage of word “Postcrossing”
Printing
Are you guys also interested in self-made (graphic design/ illustration)postcards?
Bought a membership to Zazzle to have the work of local artists and photographers printed on postcards!
Free World Postcard Day Design for countries
Etsy, Zazzle and Print-On-Demand Services
Have you ever made custom stamps?
I tried printing a postcard😊
I Just bought 50 cards on Zazzle so you don’t have to!
Postcards on Zazzle
Printing your own postcards
Receiving MyPostcard Express cards - yay or nay?
Stationery paper and postcards for download and printout
Typical Hong Kong Postcard and self-printing postcard Ideas
Where to print your own postcard-books and calendar? (and offer them online)
World Postcard Day design contest — help us spread the word!
Recycling
Cutting cardboard into postcards. What should I make?
Handmade cards using old cards. Is it ok?
Have you ever seen puzzles upcycled into cards?
Question for food box card collectors
Questions about Food Packaging cards
Recycling old calendar into postcards?
What are these food cards called?
Show us your mail art
Decorating Envelopes!
Decorating the back of your →NON-HANDMADE POSTCARDS←
Mailart from the past; some examples
Show us your handmade postcards and Mail Art
Techniques
A question about making collages
Artistamps - how to make them
CRICUT postcards
How to make postcards with perforated borders?
My embroidered papercard (tuto)
Paper Woven Postcards - Show Us
Sticker bombing on postcard
Round Robins
Round Robins for handmade cards or mail art
Mailart RR
Handmade RR
PHOTO RR - many themes
Round Robins that allow handmade cards or mail art
Goody Two Shoes Chaotic Nonsense RR
Professionally printed cards round robin!
Round Robins with specific groups for handmade cards or mail art
Any handmade cards
Handmade: Mini RR
Handmade cards: MANY THEMES RR
Handmade cards: Scandinavia x Other Countries RR
Japan & OC Lovely hand-made card: Japan & Other Countries RR
Mail art postcard in general + commemorative stamps: Cards With Stamps You Like RR!
Selffmade / handmade cards: 3 in 1 RR (3 unwritten cards in an envelope)
The artist is you! art rr
Food package cards
Food Package Cards: AD cards RR
Food Packaging: Food & Drink RR
Japan & OC Food package card: Japan & Other Countries RR
Maxicards
Homeade maxi card, food and/or drink theme: Food & Drink RR
Self-made maxicard: Cards With Stamps You Like RR!
Meeting cards
Cards from postcrossing meeting: Different Countries and Postal Series RR
Meetup Cards Signed or Unsigned but not Sent includes Virtual meetups: E.Q.T.E. RR
Meet-up offer groups: Postcrossing Meet-up RR
Photos/Self-designed/Self-Printed/Professionally-Printed
Photo cards - Photos of ships you have taken yourself: All About SHIPS AND BOATS RR
Your own photography: art rr
Self-printed weird cards: Weird RR
STREET ART: art rr
Recycling/Reusing
Cards made out of grocery lists / receipts / coupons: Food & Drink RR
Recycling: Socially Good Cards RR
Reused cards (several groups): Scandinavia x Other Countries RR
Upcycled envelopes + commemorative stamps: Cards With Stamps You Like RR!
Special subjects
Handmade bookish card: The Readers’ Journey RR
Handmade LGBTQ+ related: LGBTQ+ RR
Hand made fantasy art card: 
Dragon’s nest RR
Holidays and festivals, several groups for homemade cards: Holidays & Festivals (HF RR)
homeade food or drink card: Food & Drink RR
Magazine collage. Nonsense collage of magazine cutouts. Weird RR
Selfmade ships and boats cards: All About SHIPS AND BOATS RR
Spooky & Selfmade: Spooky RR
Sticker Bombing: Weird RR
Weird. Handmade. Weird RR
German category: ISdI - Ich Stempel, du Idee: Kreativ - RR
Tags
How do Tags work?
A PHOTO and a STORY tag
**ATC (Artist trading CARDS) tag**
Colourful handmade card tag
Draw a Picture on the Card Tag
Draw Me This Tag (List 10 Themes)
ETEGAMI tag (Handmade cards)
Favourite colour tag - Handmade cards
Food package postcard tag
Front of Greeting / Folded Card Tag
Handmade Card - Non-Handmade Card Tag
Handmade cards- Choose a subject tag
Handmade Offer Tag
Handmade Postcard Tag simple - easy - fun
Homemade Textile Crafted Card Tag
Mail Art Envelope Tag
Photograph tag
German language category: [TAG] Hand-Made-Card-Tag
Tags that explicitly allow you to send handmade cards
Christian Tag
Coloring Postcards Tag
Environmentally Friendly Tag
Gay / Lesbian / LGBT
Halloween tag
List Tag
MAXICARDS: You choose (Offer Tag)
MUSIC / MUSICALS / THEATRE / OPEN AIR CONCERTS/ FESTIVALS etc. tag
Rest of Meeting postcards tag (remaining meeting postcards) - Offer tag
Socially Good Cards Tag
Totally Weird Postcard Tag
Unusual Size or Shape Postcard Tag
Vehicles/Transportation Tag - any kind of vehicles, including traditional transportation
Yellow Tag
Your favorite song lyrics tag
German language category:
[TAG] Alles ist Kunst!
[TAG] Themen-Tag - Alles erlaubt!
Trades, Requests, Offers, Penpals, Lotteries
Lotteries/Freebies
Crafting supplies USA
Lottery Chain: Meet-up in Kaunas 4th June 2022 postcard
Penpal ads
F/21/Looking for penpal to exchange paper crafts and letters
F/23/USA- reader, animal and stationery lover looking for long-term penpals around the world
F/28/Germany - Looking for penpals who share my love for upcycling, nature, cooking, recipes, handcrafting
F/45/USA - Looking for crafty penpals for letter & paper craft exchanges
Looking for stationery addict penpals
Projects/Events
A different kind of postcard swap
Co-operative colouring
Grand Opening! Art Exhibition of Handmade Postcards!
Smail art Project
Spread Joy
–
Swaps: Handmade/mail art
(Had to be moved to the second post because this topic has become too big.)
Swaps: Meeting cards
(Had to be moved to the third post because this topic has become too big.)
Travelling Notebooks
(Most of them encourage creativity)
so you might want to update the description to just handmade, various themes. Once I bring the Holidays & Festivals group (International RR) over in January the same applies there…I will always have at least 1 group devoted to handmade cards. Many of us enjoy making them 
I somehow missed that one. Added it!