I like Clairborne Young's guides to the ICW and of course a good chart book also. As I told someone the other day I really like the Active Captain site www.activecaptain.com it's free and has lots of infomation created by cruisers themselves with reviews plus fairly good charts showing Marina's and Anchorages. I think the best time of year is following hurricane season which ends in November. The east coast portion is fairly well protected so isn't effected to badly by weather.
Where do you want to go on the ICW? There is the Atlantic intra costal waterway, the Gulf Coast Intra Coastal waterway and the West Florida ICW. The further South is best in the winter. I personally prefer the fall (this time of the year) for the Gulf Coast (panhandle). I would not say that one month is better than the other, from Jan thru April--but it will be more crowded--and perhaps more expensive. Get ready for some sticker shock if you go to marinas in the South--if you can get in. Check out various threads--including "The cruising Adventures of Wild Blue and crew"--they had some nice write up of their S. Florida's adventures.
I agree with Marvin's recommendation of Claiborne Young's guides. Also the Southern Waterway guide is an essential (I believe that the 2009 issue is due out shortly--wait for it if you can. Also "Skipper Bob" has some good ideas in his guide which includes anchorages on the ICW. (Skipper Bob died a couple of years ago, but the guides are still being published.
Claiborne Young's "Salty SouthEast" cruisers net is a very "up to date" resource: http://www.cruisersnet.net/ Be sure and let those of us who live along your path when you are coming by!
