Small but great applications are often only passed on by word of mouth, unless you find them by chance. Here's a few apps that I use myself, that others may also like.

XFCE : A nice lightweight and clean window manager <3 . Included with Slackware 12.0. Use it!

root-tail : Is able to tail a logfile just like 'tail -f', and print the output directly onto your root x window. Very useful for a sysadmin needing to monitor these things, looks pretty too. [Making it work with XFCE].

SABNzbd : A program that processes nzb usenet files, then automatically downloads the files from usenet, parity checks them with par2cmdline if installed, unrar/zips them, and deletes the partial files. All run from a nice local web interface. I will shortly be writing a guide to cover installing this on Linux.

SABNzbd Nova Theme : Makes SABNzbd look a lot better, and is more usable with this project.

mplayer : I found the xine player and browser plugin included with slackware was a bit buggy, and when resizing streaming video it would lock up on me. Instead, I use mplayer, mplayer-codecs-all, and mplayerplug-in, using slackbuilds from http://slackbuilds.org/ - search for the above there.

bwm-ng : Nice simple command line curses2 based bandwidth monitor. Does exactly what it says on the tin. Screenshot below.

gtkpod : I found this was a lot simpler to use to put music onto your iPod compared to messing around with AmaroK as is often suggested.