Also see this article series of mine called 'Top 10 One-Liners From CommandLineFu Explained'.

Top one-liners 1-10:

http://www.catonmat.net/blog/top-ten-one-liners-from-command...

Top one-liners 11-20:

http://www.catonmat.net/blog/the-next-ten-one-liners-from-co...

Top one-liners 21-30:

http://www.catonmat.net/blog/another-ten-one-liners-from-com...

Top one-liners 31-40:

http://www.catonmat.net/blog/yet-another-ten-one-liners-from...