as mentioned above, avoid Toshiba. I've had 3 and they've all sucked. Great at first then they slowly deteriorate, regardless of OS reinstalls, driver updates, etc. It's almost like the machine slowly loses the will to live.
Bear in mind, tho, that I've a friend who's owned 4 Tosh laptops and swears by them.
So far I've seen good things on the Dell laptops I've worked on.
IBM Stinkpads... meh... they're ok for taking notes and that's about it.
Also, invest in a security device or two for the laptop/bag. Seen some that plug into the USB port and a) can be cabled to a post, and b) sound a bloody loud alarm if the unit's moved. Most laptop thefts are the result of negligence ("but I just looked away for a second!"... no, you were gone for 5 minutes, and, a second's all it takes) or a vehicle breakin.