Thales Leites, as good as he is at fighting, I think he is better at teaching.
Jeremy Horn & "Charuto" Verissimo are 2 of the better ive attended.
Mac Danzig, very good teacher and makes it easy to understand
Shogun
Gokor for legs
Robson Moura for jitz
Anderson and Nogueira gave a great seminar
Serra's seminars will give you some great BJJ stuff.
I wouldn't mind taking a Mayhem MMA seminar.
4L
Renato Tavares
eddie bravo is rad.
paulson is good but shows so much its hard to retain it all.
rob kahn
Erik Paulson Shows a ton of stuff and is funny as hell.
Greg nelson and Erik Paulson FUCKING RULE........get them trust me its well worth it
AnthonySullivan - Bas Rutten
We attended a Bas Rutten & Randy Couture Seminar and were dissappointed.They were approchable and friendly but i didnt get much besides an hour of the big book of combat and a you tube clip w/ some takedowns.These guys are really "Legends" but the seminar we attended was geared for some TUFers not to aqurire tools for ones skill set.
ii'd say horn, hands down. but i guess it depends on what you are looking for.
Marcelo Garcia! Shows sooo much and makes sure that you get it.
Ray Elbe - Jon Fitch
This^^^ and Eddie Bravo
Jeremy Horn
I'm going to have to put my name in there. If not me the of course Couture
Dan Henderson