Blue Mountain Arts' Electronic Greeting Cards - The "Yahoo" of electronic greeting cards.
Egreetings - Search. Scheduled delivery. Best Sellers. Automatically sends confirmation (no choice). Cards that are sent look postcard-like. Lots of cards. Cake & Candles has a good section.
Care2 Used to be called Care-Mail Searchable. Favorites.
Amazon.com e-Cards Searchable. Schedule Delivery, Most Popular. Always sends two e-mail to you: once when sent and another when picked up (Can't turn this 'feature' off).
Yahoo Greetings - Favorites. Many are tagged American Greetings.
Say-It-With-Ease.com
Activegrams - All the cards are animated. They also advertize themselves a bit much.
123 Greetings - Still free!
Greet Someone - A lot of steps to go through (6: choose background, font, music, etc...)
greetings.xoom.com - Cards have actual front, inside & back. Not sure the metaphor translates well to the web.
Pooh's Postcards - Limited selection, and you need to paste in your postcard ID number.
Ask Jeeves Postcards
Peet's Postcard - Four postcard selection from Peet's Coffee & Tea