It all depends on your tastes I suppose, but as far as DC books I'd say top on the list over the past year or two has been Batman and Robin (by Grant Morrison). Now, the creative team is switching over (to Pete Tomasi, who is also good), but you can get Morrison's run in trades/hardcovers if you're interested. It is all very good. He has now moved over to a new title, Batman Inc., which looks great as well. I'd also recommend the Green Lantern books. Personally, I've only read the main title every month for the past few years, but I've heard great things about GL Corps and the newer Emerald Warriors as well.
Otherwise, I hear great things about Secret Six (although I don't read it), and some other titles. Superman seems pretty boring to me right now, and JLA is a mess (or at least it was when I dropped it six months ago). I do like the current Flash run, but it isn't anything like "you must read it". It has been good so far, and will be going into its own little event (Flashpoint) this year. I think all the Batman stuff is pretty decent though, at least I enjoy it enough. As far as the other DC titles, maybe someone else can shed more light. Admittedly, I mostly stick to the "big guns" (Batman, GL, Flash, Superman, etc.).