If you want something totally different then the rest take a look at http://thecardchest.com/ .
These ecards are setup in a way that looks like real life cards. They come in a virtual envelope that you open, and then can turn the page of the ecard in 3d from front, inside, to back. It lets you type and draw on the envelope and ecard also.
Maybe the best thing is that the site has no ads whatsoever...so the ecards you send won't be a cluttered mess. While all of the cards aren't free, they have select ecards that are free and I've seen them run free weekend and cheap subscription deals before.