Found this Google Chrome extension that puts those new tabs you open to good use. You get a "heart" for opening a new tab (provided you don't immediately navigate away as there are banner ads displayed) and you can donate these hearts to good causes.
They say that a new tab "generally raises between 1/10 and 1 cent ($USD) for charity." They also point out in the FAQ that "no matter what our costs are, we give at least 30% of our revenue to charity." And they release financials so that you can see where the money is going.
The extension also includes widgets like a clock, bookmarks, notes, and a to-do list for your newly opened tabs.
What you get: I don't think you get any bonuses, but it seems like a really easy way to raise some money for charity
What I get: 350 "hearts" that can be donated to causes