I've had Toshiba, Dell and Sony laptops in the past. Sony and Toshiba had the best build quality. The Sony ones were nicer looking than the Toshiba however. The Dell's had good specs for the price but weren't built as nicely. I need to get a new laptop at some point, I've currently got a Dell Inspiron 8000 at the moment.
From what people have told me, IBM laptops are good but you're paying for that build quality.