You might want to be careful when doing link exchanges on sites. Most of them are actually identified as link farm and if google finds out that your site address is listed there, they will actually consider giving a PR slap.
I go and ask for link exchanges on Digital Point Forums. There are a lot of users there and I find a lot of potential link exchangers for all the niches that I could think of. I'm not sure how google likes what I do. We actually talk about the link exchange via private messages, so I don't think theres any problem ...