The tablet PC has pretty much been a product in search of a market, despite Bill Gates’ prediction/wish for them to become much more common. I’ve never seen one in the wild and don’t know of anyone who uses one, so I can’t recommend anything from first-hand experience.
I use Newegg for most of my tech purchases, and they do have a tablet PC section, including links in the sidebar that let you narrow down the section by brand, price, screen size, etc. They also have a top sellers link which I often use when making purchases, and both of the top sellers in the tablet PC category are HPs, which I know you guys like.
Here’s Microsoft’s Tablet PC hardware page.
Depending on how small you want to go, there’s the OQO; this is more of a UMPC ("ultra mobile PC") than a tablet though. I’ve always thought the OQO would be cool to get, if I had an extra $1500 laying around, though my iPhone has filled many of the needs that the OQO would have.
The Nokia N810 is similar to the OQO, but is far less expensive: about $500. It just came out today and is available at places like Best Buy right now. It runs Linux, though, and I suspect that the software that you need to run is Windows-only.
Regarding mobile broadband: any UMPC is going to have that option, and for any tablet/laptop you can always add it later with an add-on card (PCMCIA or "PC Card" as I believe they’re calling it nowadays). You can get it through AT&T, Sprint, or Verizon. They’ll probably try to sell you on the newer faster 3G services (HSPA for AT&T; EVDO for Sprint/Verizon) but 3G coverage is pretty limited right now, mostly only available in metro areas. The older slower "2.5G" services, like EDGE from AT&T which is what the iPhone uses, have coverage pretty much everywhere you can get a cell signal. But the 3G coverage areas are expanding all the time, and they’re backwards-compatible with the older networks anyway, so 3G is probably the way to go, especially if you do most of your work in & around Philly.
