Some useful DOS programs for your DOS'ing pleasure:

TechW0rm
The ULTIMATE starting point for AUTOEXEC.BAT and CONFIG.SYS programs that use less memory (replacements etc).

MaxDIR
A colour-coded version of the DIR command that shows much more information.

CuteMouse
CuteMouse uses FAR LESS RAM than the bundled Microsoft Mouse drivers. Can even load itself in the high memory area itself without the need for other loaded system programs, neat.