I have to admit, Zombie Fortress has taken a big step, it went from 4 players max to 20 max players. Very impressive I gotta say.
I'd recommend you try Zombie Fortress out sometime, the people are certainly nice and it's great for a laugh.
Saxton Hale, it has it's downsides I feel, given all the spell spam and occasional sh*t flinging but it can also be fun.
Trade Gaming History is where all your trading goes really, as well as a few mad children who moan in chat, nothing too bad, it's pretty fun.
Jailbreak is where I personally started off, great server really. It has a solid rule base and you'll only sometimes get abusing blues, I'd recommend you try it out definitely.
*EDIT - I haven't actually tried Surf yet, so I'm not too sure what it's like over there, sorry.