Well my LS has over 80 members. I dont have an exact number but we have 73 members requestered for our forums lol.
I have seen 48 people on at one time ;). The linkshell is WindurstSpecForces on the Cerberus server and we are windurst only so i think being that big and only 1 nation says something :).
I love having a large LS because when you need help you get it. When you want to do an EF all you have to do is say guys EF in 3 hours at Odin gate. 3 hours later you have 18 people ready to go own some mobs.
I would love to see how large some of the other LS are.