Here's some of her credits:
Bleach - Franceska Mila Rose, Mizuho Asano, Shota Toyokawa, Katen Kyokotsu Tachi, Katen Kyokotsu Wazikashi, Sogyo no Kotowari A&B
Catherine – Trisha, Erica
Ed, Edd n Eddy - Nazz and May Kanker (Season 2, 4-6)
Monster High - Abbey Bominable, Spectra Vondergeist, C.A. Cupid, Scarah Screams, Rochelle Goyle
Naruto Shippuden - Guren
Persona 4: The Animation - Chie Satonaka
Persona 4 Arena - Chie Satonaka
Persona 4 Golden - Chie Satonaka
Ranma ½ – Kodachi Kuno (Season 5)
Saber Marionette J – Cherry, Luchs (Ep. 1-13)
Saber Marionette R – Cherry
Skullgirls - Parasoul
Wild Grinders - Stubford, Denise, and Patty.
Here's more information on her official website: http://erinfitzvo.com/workbio/
Also, I noticed she doesn't "currently" have any appearances listed for May, on her website.
Update: I recently spoke to Erin, and she's most likely; willing to be a guest, if asked.
This post has been edited by glenburg89: 12 October 2012 - 10:57 PM