Look at what you need, and decide on that. I decided against going Netbook and got a Lenovo X60 instead off eBay. Around 6 hour battery life with the non-low voltage CPU and an 8 cell battery, 12" LCD (old school 1024x768 which I prefer over wide screen) and around 3.5 pounds (2.98 or something with the 4 cell).
If I were to go Netbook the Lenovo S10 has an Express 34, Lenovo S12 for bigger keys (I have larger hands than some), I also considered an HP2140 which has nice keys and an aluminum case but with spending that much dough I wanted a full notebook for purposes of speed and expansion options. The HP2140 has an Express 56 slot.
For me key size was a big deal, battery life (most netbooks are good in this area with a 6 cell), but also doing anything more than basic tasks means a netbook wont be powerful enough for you. I also didn't want a glossy screen, and many netbooks are glossy currently.
If you just need a basic netbook, go to your local computer store and type on a few. See if it has enough USB ports for you, see if you like the screen, if it has a 3 or 6 cell battery - get a feel for them first. The SSD drives that come in netbooks are not fast SSDs and are low capacity to boot.
There are several good review sites that go into depth too. I came to the table needing a couple specifics so that made my searching easier.
