Help Me Decide on a Computer and Wireless Service

I'm looking at getting a laptop so I can travel from jobsite to jobsite and still access email, the server, and hopefully the internet. I'll need to get an Internet connection through a wireless provider but I think the speeds are better than dial-up. The two questions are simple. 1. Who's laptop should I buy? Our Office has Dell desktops. 2. Which wireless company should I use for service? Cingular/Verizon/T-Mobile/Sprint/Other? Please Help by adding to my comments or emailing me. My blog email is jamesguhn (at) gmail (dot) com