You can watch scooby doo episodes over at www.funniermoments.com, which in my opinion is the best FREE place to watch. And it's worldwide. Then there's also wbkids.com (US only) and of course youtube (not good quality and pretty random). A good paid solution is amazon instant video.
The best place to watch House M.D. episodes online for free is tvnuke.com. You can watch the episodes for free without any downloading or surveys and the links are almost always good. They have all the way up to season 7 episode 10.
One can watch free videos of Futurama online at sites such as Watch Futurama Online, VGuide, TVDUCK and Free Online Episodes. One can also join Netflix for free for a trial month and watch Futurama online for free during that period.