In short, Dell got out of the PDA business a couple years ago while HP reduced their line (now mostly just overpriced multimedia-focused models) and Palm has ridden the edge of bankruptcy, but now gained new hope with the impending debut of the Palm Pre. Given your minimal requirements, you may be best suited picking up an older Palm TX or Palm Tungsten model on Ebay or the like. Both use the same operating system you're familiar with, include large color screens, and have tens of thousands of applications available from years of development, including those you may currently use.
Hope this helps,
I am looking to buy a pda. I had an old palm and liked it. I want one that has a color screen, but don't know about the different brands. I don't need anything real fancy, just a color screen. My main concerns easily accessing different apps for them, and just keeping track of my fire department appointments and meetings. Everything else would just be extra. I know palm has a bunch of apps but what about hp and dell? Any suggestions or help on the brand and models would be greatly appreciated.