The Dell Inspiron 101v mini is a good entry for someone who wants to take the netbook plunge. I got it for $300 (on special) and that's almost impossible to beat. Here's why:

1. 2GB RAM and 160GB HDD. Plenty for portable needs.
2. 3 year warranty (I hate the 1year warranty on laptops and netbooks -- you can frequently replace them for the cost of just one repair, but it often increases the price quite a bit)
3. Ubuntu 8.04 preconfigured (I'll update this as soon as I get time, but the default configuration is user-usable out of the box). This includes wireless networking that actually works (I could tell...