ChaunceyK: Do you do that without a traditional cable provider? Would I still get CBS, Fox, Adult Swim, History, and TruTV with just Roku, Netflix, and Hulu Plus?
Hulu was formed by the cooperative efforts of NBC and FOX, with ABC joining later, so almost all the normal, scripted, non-syndicated programming from those three is available for free for a while on Hulu (no sports or full newscasts, though). Of the big broadcast networks, CBS is the lone holdout (though, interestingly, The CW -- which is co-owned by CBS --
does offer its programs on Hulu, as does Showtime, which is CBS-owned). Looking at
the networks that offer content on Hulu, it doesn't appear TruTV has anything, and there's only a handful of popular History shows available. Adult Swim, on the other hand, seems to have a lot of its programs on there.
With Netflix, be aware that they do not offer recent episodes from the currently running season of any show (unless you count Netflix originals -- but even there, they put up an entire season at once). In most cases, you have to wait until the new season begins to air (or would have begun, in the case of a canceled/finished show) before the previous season is added.
I know almost nothing about Roku or similar, and I've yet to try Amazon Prime.