You can mine on most computer-based platforms, from PC's to
DVR's(!), but it isn't a good idea. The amount you'll spend on electricity mining with CPU's and GPU's (for SH256 Bitcoin style mining) will never be covered by the BTC you can earn. If you want to mine a volume of
BTC you should see if you can afford to spend money on an ASIC (such as an AnyMiner or a RockMiner). Be careful of pre-ordering anything that isn't available on-the-shelf. You won't necessarily earn the money that you spend on the hardware back, but it would be a good way to learn how it all works.
If you're not bothered about actually mining any bitcoins then you can pickup Block Erupter USB's or Antminer U1's dirt cheap on ebay. You'll definitely never mine anything useful, but it's still fun.
https://en.bitcoin.it/wiki/Mining#The_mining_ecosystem