Mining bitcoin (BTC) used to be an option using graphic processor units a while back, but now it's pretty much useless (unless you need heat anyway) to mine them unless you have bought dedicated bitcoin mining hardware. An alternative, being much more reliable on memory called litecoin (LTC) might be considered an option if you still feel for mining. Here's how I set it up in Ubuntu:

Prerequisites:

• Latest drivers from ATI/Nvidia
  
• Required packages listed in cgminer's README file: I did not enable ADL for overclocking.
  
• Registration in a mining pool and a litecoin wallet with your receiving address (you might try to go ahead alone if you feel lucky)
  

git clone https://github.com/ckolivas/cgminer.git # run from /tmp
./autogen.sh --enable-scrypt # from inside cgminer folder
sudo make install # Installation...

Then run cgminer:

cgminer --scrypt -o stratum+tcp://coinotron.com:3334 -u user.miner -p password --intensity 12

A higher intensity can be used if you are not going to be working on the machine. A fairly new, although budget graphics card ATI 7850 gives me about 260Kh/s (Kilo hashes per second) resulting in about 0.7 LTC per 24 hours.