Get PocketMVP, great for playing divx, ogg, mp3, etc....
An awesome program you should buy is Omega One Battery Pack 2003, it has a lot of great utilities on it.
I believe there are free overclocking software for you model that should boost your PocketPC speed from 400mhz to 472mhz. I think it is called hackmaster or something.
edit: Another great overclocking software
http://www.immiersoft.com/
"The speed can be scaled from 100 to 300MHZ on the fly for the iPaq 1910 ,100 to 500MHz for PXA250 XSCALE processors and 100 to 530MHz at 265MHz bus for PXA255, PXA26x, and 104 to 728MHz for PXA270 or higher processors. Use the Auto Scaling capability of XCPUScalar and assign your own speeds to different CPU loads as shown in the picture above. With Auto Scaling, applications will get power on demand depending on CPU usage, saving battery life. Monitor CPU usage as you run your applications, XCPUScalar integrates with popular task managers like Wisbar, Icbar, and Gigabar. Monitor the health of your Pocket PC using the health meters. iPAQ 1910 users can almost double their framerates when watching movies or playing games. "
I basically overclocked my ppc for emulators(especially psx emu).