<< ok, there's a $40 cable that'll hook two computers via USB. looks like it'll run fine for games, file transfers, etc.
can i get a PC nic, a pcmcia nic, and cable that will beat that? >>
You can get 2 10/100 PCI nics for like $10 each and a crossover cable for $5.
But one of your computers is a laptop? Laptop nics do cost a lot more, but still you should get the laptop nic, PCI nic, and the crossover for $50. It will be about 10 times faster.