http://www.alloscomp.com/bitcoin/calculator.php  http://www.alloscomp.com/bitcoin/old_calculator.php  http://blockexplorer.com/q/getdifficulty  http://blockexplorer.com/q/nethash  The very last page, proves that as bitcoin mining loses its popularity, the rewards from it are easier to obtain, in the last two block  difficulty changes, the difficulty has dropped an entire 8%. and it's been going down for a bit now.  edit: I check all of these numbers daily.