All 13 episodes, complete, uncut, free and legal. It's online at The Adult Swim Fix but I don't know for how long. A week or so? I've never used the Fix before so someone can feel free to correct me. Point is The Venture Bros. is a killer show, so take advantage while it's free and on demand.

Oddly though they have some of the episodes out of sequence. The first episode is Dia de los Dangerous and it goes in order from there, but the final three episodes should be Past Tense, The Trial of the Monarch and Return to Spider Skull Island. Watching those three out of sequence would be pretty bad.

Oh, and don't bother with The Terrible Secret of Turtle Bay. That's the pilot. And it's a pile of ass crap.