Suggest you make sure there is wireless communication built in. Most will have it these days but worth checking. 802.11g is the preferred protocol.

My Toshiba Satellite M-20 S257 has been very satisfactory for the last 9 months. Good battery life, excellent 14" screen, and pretty light weight. This model, if you can find it, is primarily made for the business market and comes with Windows XP Professional standard. Downside is it comes with little in the way of application software as is is assumed the business already has bulk licenses for things like spreadsheets, word processing, and email. Mine cost only about $1200 and may be cheaper now that it's an "older model".