Merlin, naturally. Supernatural too. Oh, and The Sarah Jane Adventures.
Other than that, most shows that I'm interested in, I'm way too far out of sync with them to be concerned whether they're coming back in the US! Which is terribly, really, but basically it boils down to:
Fringe - still watching through season 1 in order from the DVD, and keeping up with repeats of Season 2 on Sky 2.
Chuck - Season 3 still airing on Virgin. No idea when season 4 starts, either in the US or the UK.
Leverage - Season 2 airing on Bravo. I think season 3 has already started (and possibly finished?) in the US, but I'll worry about that when I've finished season 2.
Stargate: Universe - pending whether or not I like the DVD of season 1, I expect I'll try to catch season 2 whenever it starts airing over here.
White Collar - I've still only seen the pilot, but like Matt Bomer enough to try to catch more of it. Unforunately, no UK channel seems to be airing it at the moment. Which is a bit :o(
V - only caught the first batch of 4 episodes, but I keep meaning to check out the remainder at some point, and that's back for a second season, isn't it.
And a brief RIP for Heroes (although I never properly watched season 4) and FlashForward (which I adored, why did they go and cancel it? Grrrr...)
So, yeah. I seem to be watching way more US telly than I used to. I blame Sarah for introducing me to the wonders of Sky+, and Rita for having a Sky+ box so I could keep up the habit.
Of course, the absolute highlight of the next few months will I hope be the Doctor Who Christmas special... No change there, then...