uncommon linux / bash commands worth using

linux-bash-tips.txt

you can pipe stuff through ssh -- e.g., concatenate your SSH key on another host.
cat ~/.ssh/id_dsa.pub | ssh me@remotebox "cat >> ~/.ssh/authorized_keys"

lsof - http://danielmiessler.com/study/lsof/

disown (detach from process so when close your terminal it doesn't get killed -- like doing nohup in advance)
xargs / parallel
sudo !! -- repeat last command with sudo prepended
!$ -- last argument to last command
!* -- all arguments to last command
!:s/foo/bar -- redo last command replacing first instance of foo with bar
!:gs/foo/bar -- redo last command replacing all instances of foo with bar
nc -- network communications stuff -- can do things like this:
     on box1:   tail -f sslerror.log | nc -l 9999
     on box2:   nc box1url 9999

and on box2 you'll get a stream of the error log