Legacygames.com has a huge library of casual games for sell. You can also download demos of the games.

This game portal is from Legacy Interactive, who are responsible for such casual games as The Apprentice and Law & Order. Plenty of titles to choose from and new titles to be added daily.

Check out their blog which features some reviews of the games on their website. You can submit your own review and if they use it, get $25.