I am using a Dell Inspiron 5150 laptop, everything works great except the modem, which I did get working after paying $15 for a linux modem driver.
I also know that Compaq (part of HP) is starting to sell laptops with linux preinstalled - even if you did not want linux preinstalled, I am assuming these would be very compatible with linux - SuSE in particular. I think the model is called NX5000
sells laptops with linux presinstalled, as well as dual boot options.
as far as minimum specs, this probably isn't a big deal, if it can run XP it should be able to run linux, although make sure to get enough Hard Drive space for the two installations.