When you read about bitcoins, you'll stumble over the possibility to "mine" them. This consists in participation in the bitcoin exchanges by helping with the calculations.
As a low level technology enthusiast, I couldn't resist to give it a trial. Here my experience and view:
CPU based bitcoin mining isn't efficient, even using a rather highend multicore processor. The power bill will be much higher than the value of the bitcoins earned (besides the environmental side effects). I've just tested the calculation rate and dropped immediately.
GPU (Graphic Cards used as Processor Unit) based mining seems to be able to reach break even, if you run it while running the computer anyway. However, earnings will be very slow, unless you got one or multiple top notch graphic cards. As an example; with my lowend Radeon HD5450 graphics card (thermal design power 20 W), I've mined in 3 days 0.003 bitcoins (3 mBTC), worth right now a little less than 0.5 USD. With a Radeon HD 7970 about 40 times that result can be expected, without being much more efficient. Nevertheless you might want to give it a trail, if you got a highend graphics card anyway.
Then there is bitcoin mining using specific hardware made ONLY for bitcoin mining. Something I haven't tried out, as it requires an important upfront investment:
FPGA (Field-Programmable Gate Array) seems to be the current way of bitcoin mining. However their obsolescence is announced with the arrival of ASIC based bitcoin miners. It doesn't make sense to invest into this now, it is too late.
ASIC (Application-Specific Integrated Circuit) based mining is announced as the ultimate (hardware) evolution in bitcoin mining. I didn't find any consumer priced solutions shipping right now, though.
Read more for example there > https://en.bitcoin.it/wiki/Mining, there about hardware > https://en.bitcoin.it/wiki/Mining_Hardware_Comparison
Finally, solo mining is something like a big lottery with a very low chance to be the lucky winner, means you might mine for years without any reward. Therefore it is recommendable to join a mining pool (or create your own pool, if you got knowledge, money and time) where the efforts of thousands of miners are joint and the rewards are dropping in more steadily and are redistributed following different schemes. That is where my 3 mBTC are accounted at the moment.
Read more there > https://en.bitcoin.it/wiki/Pooled_mining and > https://en.bitcoin.it/wiki/Comparison_of_mining_pools
I guess deeper discussions about bitcoin mining belong into the "Technology Stuff" section of our forum