One of the sites that I always forget to mention is Recyclebank, whose “hook” is that they teach you about recycling. They pay for rewards by partnering with major brands, but that’s okay, we don’t judge.
One of the nice things that they have done is move all of the “earn” opportunities onto one page, meaning that you don’t have to hunt all over the site to find them. There are well over 1,000 points available, so I gave up counting. Most of the time, you earn points simply by clicking on the page or, at worst, clicking through a few pages. The prizes aren’t terribly exciting, but decent stuff pops up on occasion.