Baseball HQ - A lot of free baseball information, plus subscription material and two books for sale. Dr. Stats - The good doctor offers free newsletters for baseball, football, basketball, and hockey.
More info is available by subscription.
This is one of the top-ranked newsletters, issued weekly, but they also offer a lot of free information, including quarterback biorhythm reports. Fantasy Football Today - All free information, including injury reports and a good assessment of matchups. They also sell several products by subscription. Fantasy Sports Publications - There's some free stuff here, but the emphasis is on selling their publications, which I've heard are excellent. Grogan's Fantasy Football - Some free offerings, primarily injury reports, and several products for sale.