I'm currently running Fedora Core 4 on my 14" Thinkpad T42p. 2ghz, 2GB RAM, 802.11 A/B/G, gigE and bluetooth, 1400x1050. DVD-RW is an option. Only problem is weight: with the 9 cell battery, mine is around 6 lb. Not sure if a smaller battery is available or not.
This was work-issued so I didn't have a choice in the matter but for a main development machine, I think I'd want a somewhat larger display. 15" would be preferable IMO.