It would depend on your budget & what exactly you want to do.
Wireless gear is expensive right now as compared to wired where the only requirements are Network card,a hub/switch depending upon how many computers you want to connect & UTP CAT 5 of appropriate length.
Si incase you dont need the wire clutter & have got the money I would suggest getting Wi-Fi 802.11g compliant equipment.
There are various options available to you for setting up a lan like in case you just want to share resources you could get 2 802.11g network cards,hook it to the two computers & configure a Ad-hoc mode.But this kind of network hampers performance as more computers are added in the ad-hoc mode.
So please tell us your requirements & what exactly are you looking for.