With wireless LAN, there are 3 different types. They are 802.11a, 802.11b, and 802.11g. Now, 802.11a hasnt been really around for quite a long time, but 802.11b has been, and is still in use quite a bit. 802.11b only gives you 5.5 or 11Mbps speed though, so it isnt too fast when compared to Wired LANS.
However, 802.11g is the new one out, which supports speeds up to 54Mbps (and even 108Mbps if you have devices that support it).
802.11g is the new standard, and is usually backwards compatible with 802.11a/b, so you shouldnt have any problems.
So, in short, go for the 802.11g.