Some cool bash/Linux stuff:

If you're using bash, put a line TMOUT=600 in /root/.bashrc. The user will automatically logout after 10 minutes.

If you're often cd'ing into a mounted directory, this might mean a lot of typing. For instance, at a client I always have to change to directory /mnt/es-groups/EWII for the project files. To shorten typing, I created the following line in my .bash_profile file:

export CDPATH=".:/mnt/es-groups/EWII"

When you type cd Documents, you'll find yourself immediately in the project's documentation directory; bash even tab-completes.

UNIX Commands No One Ever Heard Of ™...: Type script and press enter. A new shell will be started. Now do whatever you like. When you're done, press CTRL-D on an empty prompt. script will reply with something like Script done, file is typescript. The new file will contain whatever you've typed, including screen output! Fun to put in your friend his/her login scripts....