Catcoin is crypto-currency, similar to Bitcoin and Litecoin. It uses Scrypt as Proof-of-work algorithm.
It can be mined on a CPU, or more effectively on a GPU. There is no (known) ASIC or FPGA miner currently for Scrypt.
Some technical information about CatCoin:
Block reward: 50 CAT
Block time: 10 minutes
Retarget: 36 blocks (roughly 6 hours)
Max supply: 21 million
Reward halving interval: 210000 blocks (roughly 4 years)

Source code

Windows client

SHA256 hash: c0248907be0c92da0302f1fd573d6a20f5eefbb443c2b5c51670eaca0f985dea

Rar file (portable) :
SHA256 hash: 379f4d68c0cd28918a47c817d373180a2515de7bf385f261b45212897562704f

Block explorer

Original thread at bitcointalk, including list of pools

Trading CatCoin

Catcoin can be traded on following exchanges:
Cryptsy119 Active Markets
Coined Up56 Active Markets
CoinEx70 Active Markets