I haven't messed around much, but in the build I got from a friend I could use Airport without any problems. I clicked on the Airport Strength dock thing and got a menu. There was a choice called "Create Computer to Computer Network" or something like that. I don't have two airport compatible computers, so I didn't try it, but that's probably what you're looking for.
I've got an Airport network set up in my house and a G3 PowerBook running OS X. Installed it, clicked over and set a few networking settings (DHCP) and poof! It worked! The only problem I had was that on reboot OS X wanted to default to the modem and my TCP/IP connection...it drove me nuts until I went into the "advanced" settings and unchecked both modem and built-in ethernet (leaving Airport selected). Works fine now...in fact, t feels like its faster than it was with OS 9.1!