Yahoo has built up their fantasy games through the years, and football is their best. If you havent been there in a while look for their drag-and-drop features for roster moves. There is a section for advice and the option to link your roster to your cellular phone for updating scores.
This is my personal favorite as its free and its you and/or your league against the rest of the country and they rank you weekly on how you stand up against all league members. Check out all the mock drafts they have going to guide you in your own picks.
This site has live scoring updates, enhanced scouting tools, mock drafts, and draft-room improvements.
This site has the most info of any site listed above. If you want to win big prize money, this is the place to be.
If you guys know of any other helpful fantasy sites, please list them below.