You can also invest in mining shares.
Asicminer pays out nice dividends (40% per annum!) and they have proved to be trustworthy. They also sell their own designed hardware so they don't only get income from mining.
Their shares are available at Bitfunder.com, Btct.co and Havelockinvestments.com.
To me it makes more sense to buy these than spend the money on a mining rig. Unless you already have a high end gaming PC and cheap electricity. You have to earn back the cost of the rig and the hardware depreciates in value. Whilst the Asicminer shares may appreciate in value (or maybe not). It's the dividend I find interesting though.
Disclaimer: I hold several of these shares. Do your own research to see if it is a good investment to make. Both buying and operating a mining rig and buying shares are an investment which you may or may not redeem.
That´s exactly what I was looking for. Thank you so much!