(the first 3 have very useful templates to speed things up; full credit to Emperor)
CSI at the International Movie Database, great for lists of writers, directors, special guests and other miscellania, but a bit light on plot depth. You could use the summaries in lists of episodes, however.
TV.com, a website with a broad range of information but little depth. It also has a modest photo gallery which you may find useful.
CSI Guide, contains in-depth plot information, but the grammar and syntax is a bit dodgy (for "a bit dodgy", read "incomprehensible")
CSI Files, well written plot synopses and my (Editus') first choice for plot summaries