The Linux Cookbook: Tips and Techniques for Everyday Use
I just love cookbooks. A cookbook doesn't have to be about food you know. This one is about little useful tips on how to use your Linux computer.
From this I learnt how to find all really large files which is useful if you want to find out why causes your harddrive to be so surprisingly full:
$ find /usr/local -size +10000k [RET]
$ du -sh Documents