rdiff-backup is awesome. It's a POSIX backup tool providing a (possibly remote) mirror and an incremental difference history (should that be decremental history?) of the mirror.

BackupNinja (website currently down) is even better. It's a curses (ie text based) wizard for setting up a number of backup tools including rdiff-backup and mysqldump. It does all the fiddly bits like handling ssh keys and setting up cron jobs.

Emacs, some love it, some hate it, and once in a while I stumble on something I wish I'd found years ago. I thought I'd share some of the packages I use, partly so I don't forget!

• debian-el contains a major mode for editing sources.list, as well as an interface to apt for the truly emacs centric. Also has useful support for bug reporting and bug numbers...
• emacs-goodies-el lots of toys, and of particular interest and use to me, a major mode for apache configuration files and color-theme which is somewhat self explanatory

In a debian like system this can be accomplished by:

dpkg -S $FILENAME

Of course if you're looking for which package owns a command, 'which' is your friend, the following tells me which package owns 'ionice

dpkg -S `which ionice` 

I found this article on cleaning out debian based systems. It's kinda useful.