There is a new coin called Yenten that is CPU only and growing popular. You can get a good hashrate with even fairly old computers including laptops. I'm mining it on two laptops and a pretty powerful desktop all running Linux, so you should have no issues. Check here:
https://bitcointalk.org/index.php?topic=2329470.msg23686620#msg23686620for more info and a link to the Github page to download the wallet/miner. You will need to compile both from source but there are instructions given.
have some linux server with no usage at the moment (since today) lying around here in the office. with a very good cpu, but bad gpu. so I'll give it a try. if something comes out of it, i'll report it here