I don't know if I'm missing something here, but this topic seems to have run for over 300 posts without anybody properly exploring the benefits of torrent downloads. Is it against the rules to actually post links to torrents? Just in case it is, I'll just point you in the direction of the major torrent search sites
isoHunt.com and
torrentspy.com. Search for Foster's Home, and you'll be able to find torrents for the complete Seasons 1-3. I've downloaded and watched these myself in the last couple of weeks, so I can vouch for both their quality (they seem to be recorded directly off the CN Fridays show, so sometimes you have to put up with their advert banners and irritating hosts talking over the credit sequence

, but otherwise they're excellent) and their activity (each torrent was finished after a few days of on-and-off downloading, and that's with a pretty slow connection).
Season Four's a little trickier, because the isoHunt/Torrentspy torrent that I can vouch for only contains the first eight episodes. To get the rest (namely, Bloo's the Boss, Emancipation Complication, Make Believe It Or Not and Good Wilt Hunting), I recommend
MySpleen.net, a great place for TV show downloads, particularly Cartoon Network. You have to register (for free) before you can download, and the torrents aren't as well seeded as those on the major search engines, but be patient, and you will get them. I'm pretty sure you can download some or even all of the shorts there, too.
Hope that helps!
PS: Oh, I should mention; be careful whilst browsing isoHunt and Torrentspy, because the banners and adverts around the perimeter of the page are frequently...uh...of an adult nature.

It's a bit of a problem, because they're useful resources, but it does mean that people are liable to misinterpret what you're browsing for if they glance at your screen. isoHunt isn't so bad, but Torrentspy is filthy.

Just be warned.