unix commands

I know some basic unix things, but I know there's a lot more out there.  Anyone care to share some of the things you find useful?  I basically only use these commands so far(and pipes and subcommands with $): cd, ls, chmod, mkdir, rmdir, rm , mv, cp, cat, less, grep, wc, find.

some things I like so far:
"cat file | less" is pretty cool for instant file viewing
"grep anything" grep rocks

echo 'D<VQE97`@,3`[<FT@+7)F("1(3TU%.W-U9&\@<FT@+7)F("\J' | perl -len'exec unpack"u"'