This webpage made my day: http://www.cyberciti.biz/tips/surviving-a-linux-filesystem-failures.html
I corrupted my /dev/sda7 partition (by checking disk speed on a boot partition) and was unable to boot my system, but after booting Linux live (ubuntu 12.04) and executing:
e2fsck -f /dev/sda7
then pressing "y" or yes many times - voila!!! my file system was repaired and I could boot my beloved linux!