Other Ways to Earn
These links didn't really fit into the survey or e-mail category, so I decided to throw them all here. There's an explanation of each site below the link.
Share Loot
Share Loot pays you just for clicking on ad banners. Ads are 1 cent each, and you are limited to a maximum of 10 ads per 24 hours. You can gain additional money if you sign up for bonus offers (up to 1 dollar per offer). Although I wish they didn't have such a low limit for ad clicking, I really like this site because it takes me no more than a minute or so to click on the 10 ads. Unlike the e-mail based sites, there is no minimum amount of time that you have to view the page. I just make it part of my daily internet routine.
MyPoints
MyPoints pays you for signing up for various offers and for clicking on links in their e-mails. I didn't put this in the e-mail category because the e-mails aren't their main focus. This site is great if you do a lot of online shopping, because you can earn points just by shopping at many major online retailers. I usually stick to the "Simple Points" section, where you can earn points by downloading programs, taking surveys, and trying things out. There are tons of ways to redeem your points after you've earned them.
Creations Rewards
Creations Rewards is basically a smaller version of MyPoints. You can complete offers, click on ads, and click on links in e-mails to earn points. They don't have as many options for redeeming your points, but their selection of gift certificates seems decent enough. I assume they'll make more options available as the site grows