Wizzley: My favorite next to HP, though I only have a couple of articles up. It's a very good-looking site with a small but cool community. You can use a whole bunch of different affiliate programs there, which is nice.
Infobarrel: Another great community. Owners are pretty on-the-ball. You earn based on impressions, similar to here at HP, and you can use your own Amazon affiliate links.
Squidoo: It's anybody's guess what is going to happen to Squidoo from here. Now might be a good time to build up content there for the resurrection of the site, or you may want to stay away until you see what happens. Personally, I love the site, but I don't dig their payment methods so much. There is something about being put in a line and paid based on my ranking that doesn't sit well with me.
Zujava: I haven't written anything there yet, but its a cool site that a lot of people are excited about. I'm a little turned off by their revenue sharing model, which is similar to Squidoo's.
Seekyt: Another site worth checking out. I don't know much about it, but a lot of people say good things.