You can via Firewire. Unreal Tourament is the only game out there that supports it currently. You need two TVS/TWO PS2S/TWO UNREAL TOURAMENTS/ Cables/ and of course the hub itself.
Think of it like the highly annoying link cable for the PSone. Unless, you know a bunch of friends who have the stuff needed, and plan on throwing a party, its pretty much useless.