Im a firm believer in a secondhand business grade laptop, rather than a new consumer one.
Im running a lenovo X60, dual core 1.8gig. Was about £60 from ebay and a battery for it was about $15, its got a 1024x768 screen, magnesium chassis and lid (so it'll take the knocks getting kicked around the garage floor) and its nice and fast. Buying now I'd probably buy a X61 or X200 so I wasnt stuck at 3gb of ram, but if you want to stay 32bit that caps you anyway.
for example:
http://www.ebay.com/itm/Lenovo-Thinkpad-X60-Core-Duo-T2400-1-83GHz-2GB-60GB-12-1-IBM-/141342739429?pt=Laptops_Nov05&hash=item20e8af0be5