Dave... Suggest you get a copy of Skipper Bob's guide to anchorages along the ICW and also perhaps his ICW marina guide. The first also gives you bridge and shaoling info. Skipper Bob
Others will be better than I can be on advice for the gulf but there is fairly extensive info on the East Cost portion over on the ICW thread under cruising. Take a look and then ask any additional questions you have.
EDIT... Also check out this online guide to ICW marinas...Intracoastal Waterway Facilities Guide