So you bought a mining rig. You're all pimped out at 3 G/hash but still have that itch for more but buying another rig is not an option.
Introducing.... Proof of Stake!
https://en.bitcoin.it/wiki/Proof_of_StakeProof of Stake allows you to create coins within your wallet, without having to use any of your hash power. Simply open your wallet a few times a week and BOOM! Extra coins at your disposal.
Couple POS coins for those unaware:
Peercoin - $4.41 USD/PPC
Novacoin - $7.28 USD/NVC
These coins are established and have been available for quite some time. Want to get on the POS train early??
MINTcoin
Hobonickels
GalaxyCoin
and more can be found here in StakeHunter's thread:
https://bitcointalk.org/index.php?topic=458726.0Enjoy!