There are a few different models that use the PalmOS (such as the Palm, Handspring, some different Samsung cell phones, etc). All good units and the Graffiti language is very easy to use. They have B&W and Color units as well.

But if you want close integration with the desktop, you'll probably want a PocketPC device. You can transfer files with Word, Excel directly back and forth (there are ways to do this with Palm as well).

However for the stuff you mentioned, all will work. These are pretty basic PDA functions.

But, the best of breed right now is Compaq's top of the line (MSRP $650) H3840. Has the built-in Bluetooth (ok, not a reason right now, but someday... or so we're promised) plus all the applications. And with a small microdrive you can put some major league data in it.

Saw a neat demo with wireless broadband and the IPAQ. Sending TV quality streaming video wirelessly to the IPAQ. Amazing stuff.