Here's who I've met, and who I'd like to meet. I'll post links to stories of when I met VAs as the stories are done.
Original TMNT Series
Townsend Coleman - Michaelangelo

Rob Paulsen - The original Raphael

Cam Clark - Leonardo

Renae Jacobs - April

Pat Fraley - Casey Jones, Baxter Stockman, Krang and more!
Online: Sent Barry Gordan emails (no reply).
Movies
Robbie Rist - Michaelangelo TMNT 1, 2 & 3!

Corey Feldman - Donatello TMNT 1 & 3

Michael McConnohie - Tatsu TMNT 1 & 2

Mikey Kelly - Michelangelo TMNT 2007

Mitchell Whitfield - Donatello TMNT 2007

Nolan North - Raphael TMNT 2007

James Arnold Taylor - Leonardo TMNT 2007
Billy West - Jersey Devil TMNT 2007
Grey DeLisle - Additional voices TMNT 2007
Quinton Flynn - Casey Jones original voice, replaced TMNT 2007
- Done email with Adam Carl - Donatello's voice from TMNT 2.
The Next Mutation
Matt Hill - Raphael

Kirby Morrow - Michaelangelo

Michael Dobson - Leonardo
Brian Dobson - Dragon Lord
Scott McNeil - Bonesteel. (I know he's not really a VA in this show since he's the actor and voice... though he's a VA on many many animes.)
4Kids TMNT
Wayne Grayson - Michaelangelo (even a guest here on TMNT-L)

Sam Regal - Donatello (a member here on TMNT-L)

John Campbell - Raphael

Michael Sinterniklaas - Leonardo

Darren Dunstan - Splinter

Marc Thompson - Casey Jones

Veronica Taylor - April O'Neil
Scott Willaims - Baxter Stockman
Mike Pollock - Garbageman and Jack Kirby
Megan Hollingshead - Sidney
Ed Paul - Ultimate Ninja
Sean Schemmel - Nobody (and many others)
Dan Green - Mr. Mortu, General Mozar and the Professor.
Tom Wayland - Jammerhead
Nickelodeon:

Greg Cipes - Michelangelo

Rob Paulsen - Donatello
Now who do I still want to meet? ALL the VAs from every area! With Anime North I'll be meeting two I haven't met before. I love getting to meet VAs and will keep looking to meet more.
Interested in others feelings on this and who they've met. I'll be adding more to this list as time goes (like all the other areas, I won't post a new reply just add it here with editing the post).