$@M already suggested www.atptennis.com which is very good for player interviews, head to head and other sorts of statistics, but you can also try www.itftennis.com.

The ITF site is a little more in depth when it comes to player head to heads as it includes qualifying matches, something the ATP site does not do.

Another good thing about the ITF site is that you can check players juniour records. This can be very handy if there is a player that is fairly new to the tour and you want to find out how they have done on various surfaces.

Personally I think the best way to make money out of tennis is to become very familiar with the lesser known players. The top players are always going to be made very heavy favourites, but the lines seem to be a little bit looser when it comes to the players people are unfamiliar with.

Hope that helps.

Sparks