Hi5 goes 100%
The past couple weeks I've been lurking on the #Hi5dev channel on Freenode, where most of the Hi5 team has been as well, dutifully answering questions and getting general developer feedback. I highly recommend following their developer blog where Lou (pictured here) has been posting regular updates and all the important things that you need to do in order to get your application viral, approved and reaching Hi5's users.
Some of the applications we've launched include: Top Friends, Slide TV and SuperPoke. Of course, if all you want to do on Hi5 is be friends with me, you can find me here :).