There are two seasons of Sleeper Cell, eight episodes each. They were both presented over the course of a single week, Sunday to Sunday, on Showtime. The first season is now available on DVD, and I'm sure the second season will be available on DVD soon. I highly recommend it.
If you're looking for another broadcast network program that is in the same general vein as '24', look at The Unit. It is episodic, instead of a full-season arc, but for many folks that's a good thing. You can miss episodes or see them out of order without much problem. The Unit is also much more realistic than '24' -- not cartoonish at all.
Some of the FBI-related shows are close to '24' and The Unit -- NUMB3Rs and Criminal Minds, specifically. Both are episodic as well, though, and none of these (The Unit, NUMB3Rs, or Criminal Minds) have the kind of "hold your breath" thing going like '24' and Sleeper Cell. The only other show that I've felt that with recently is Day Break (which, unfortunately, was cancelled).