The Humble Mozilla Bundle offers a ton of browser-based games at low prices, with no downloads required!
Right now you can pay what you want for Super Hexagon, Aaaaa! for the Awesome, Osmos, Zen Bound 2, and Dustforce DX. If you pay over the average price (currently $5.03 USD) you can tag on Voxatron, FTL: Advanced Edition, and one more game that has yet to be announced. If you pay $8 USD or more, you can get all of those games plus Democracy 3.
Humble offers games at pay what you want prices, and puts a portion of all payments towards charity! As always, customers can adjust their payments to split it between charity, game developers, and Humble tip.
Check out the Humble Mozilla Bundle here: //www.humblebundle.com/