Linux-On-Laptops is a good resource, problem is very few of the models currently being sold have entries at LOL (heh).
A fourth option is to watch for a used model that is known to be well supported by existing drivers. This is also the most frugal route, which has a strong appeal.
Will this situation ever change? It could get worse -- the laptop market is growing faster than the desktop market, and the fastest growing portion of the desktop market (I'd bet), "slim" PCs, I suspect has more components in common with laptops than full scale desktops (meaning much worse Linux support).
Arrgh. What a PITA.
Last 24hours, coded in Java, XSLT, SQL, Tcl, Perl, Bash. Hadn't really thought about it before, but such juggling of multiple languages in a single day isn't atypical. For the most part it's a case of using the right tool for the task at hand, though I'd love to replace Tcl and Perl with Ruby. Also glanced at Pliant, E and Haskell for my own amusement.
My computer can beat up your computer. - Karl Lehenbauer