Paperless Post is the gold standard of paperless invitations. The "stationery" and motifs are so gorgeous and realistic; you can almost feel them in your hands. 30 "stamps" (required to send the cards) costs $5, but buying more results in savings. Though the tracking options are basic, the aesthetic superiority of the cards makes Paperless Post my top pick
The Etsy of the online invitation world, Pingg allows artists and designers to upload their original card designs and gain recognition for their talent. You can also set up an event web page, upload post-event photos and videos, link gift registries (helpful if you're planning a shower) and it has a place where your guests can sign up if the party is a pot-luck. Amazingly all of this is free, but guests are subjected to ads when they receive an invite. If you prefer an ad-free invitation, a $10 membership will allow you to send up to 2,500 ad-free invites at a time.
It has literally been years since I've used Evite, but I thought I'd take a look and see if anything had changed. Well, suffice it to say, I was pleasantly surprised to see that Evite has indeed been updated with some very nice invitation designs! The tracking options are the same, but they now have party planning suggestions and a party supply store. It's still free and, therefore, definitely worth a second look.
A one-stop party planning shop, Punchbowl will help you select a date for your party (with input from your pals), suggest local vendors, and print up event T-shirts! The organizing is free, but if you want ad-free invitations, you'll have to upgrade to a Premium Account for $49 a year or $7.99 a month (you can cancel at any time).
Do you know of any other fabulous online invitation sites? Are you pro-online invitations or do you prefer doing things the old fashioned way?