I made a calculator on Excel to see how much you could make mining over the year.

It takes everything into consideration. But you have to estimate the what the difficulty level will increase to. I have no idea what the difficulty will be when all the ASICs start to ship, probably 30-40% like it did a few months back.

By fiddling around with the numbers a bit, I have put myself off mining!

Have a play around, and tell me if you think there are any improvements to be made.

I believe it is a more accurate estimate of your return than a site such as: http://www.bitcoinx.com/profit/ as it takes the increase in difficulty into account over the year.

Anyway, here is the link to my calculator:
http://www10.zippyshare.com/v/11385398/file.html