Depends what you want to promote, but my favorites are cj.com and shareasale.com. Those are a couple popular networks. Try a Google search for Affiliate Network and I am sure you will find a ton.
There's really no alternative that pays nearly as good as adsense can when it comes to that type of ads. I would go for CPA netowrks such as PeerFly if I didn't have Adsense.
I personally like Maxbounty as well, if you have a decent website and can explain how you are planning to attract visitors you will be accepted. CJ is also good, as it approves new users instantly, though there are not that many offers.
Thanks for the comments! In addition to PeerFly, I recommend checking out the following networks: AmpedMedia COPEAC Market Leverage Cutting Edge Offers Neverblue Affiliate.com W4
Amazon Associates is also good. You can sell books, video games, clothing, software, laptops, tablet PC's, shoes, MP3's, toys and much more.
10 Best Affiliate Networks 1) Commission Junction (www.cj.com) 2) ClickBank (www.clickbank.com) 3) LinkShare (www.linkshare.com) 4) Affiliate Window (www.affiliatewindow.com) 5) Amazon (www.amazon.com) 6) Shareasale (www.shareasale.com) 7) Google (www.google.com/adsense/) 8) LinkConnector (www.linkconnector.com) 9) CPA Empire (www.cpaempire.com) 10) Independents