Johnny Yong Bosch starred in Trigun as Vash, Bleach as Ichigo, Claus Valca in Last Exile, Kiba in Wolf's Rain, and Persona 4 as the MC/Toru Adachi.
Crispin Freeman starred as Alucard in Hellsing, but he also played Alex Rowe in Last Exile, Hideki in Chobits, Kyon from the Melancholy of Haruhi Suzumiya, and Itachi Uchiha in Naruto.
Wendee Lee was Faye Valentine in Cowboy Bebop, as well as Azusa Fuyutsuki and Mrs. Sakurai in Great Teacher Onizuka, and Haruhi in The Melancholy of Haruhi Suzumiya.
Vic Mignogna starred as Ed in Fullmetal Alchemist, the creepy lawyer in Nerima Daikon Brothers, Tamaki in Ouran High School Host Club, Takenaga in The Wallflower, and Death Scythe in Soul Eater.
Justin Cook starred as Yusuke in Yu Yu Hakusho. John Burgmeier was Kurama, Christopher Sabat was Kuwabara, and Laura Bailey was Keiko. Later on, all four teamed up again for Fruits Basket (Cook as Hatsuharu, Burgmeier as Shigure, Sabat as Ayame, and Bailey as Tohru). Sabat is also known as the voice of Vegeta in DBZ, Bailey currently stars in Soul Eater, and Cook's cousin Aaron Dismuke not only was Hiro in Fruits Basket, but starred as Al in Fullmetal Alchemist.
Luci Christian starred alongside Chris Patton in Full Metal Panic!, and joined him again in Nerima Daikon Brothers. Patton has most recently done work for The Wallflower, Welcome to the NHK, and Soul Eater.
Yuri Lowenthal is married to Tara Platt, and they team up often. Recently, Lowenthal starred in Persona 3 as the Main Character/Pharos/Ryoji, and in Persona 4 as Yousuke. You might also recognize Lowenthal and Platt from Naruto, as they play Sasuke and Temari respectively.
Melissa Fahn was Ed in Cowboy Bebop, as well as Gaz in Invader Zim. She's related to Jonathan Fahn, a.k.a. Jonathan Charles, the voice of Yusuke in the Yu Yu Hakusho movie (but not the anime) and Tom Fahn (a.k.a. Tom Charles, whose most recognizable role is Sho in Guyver). Tom is married to Dorothy Elias-Fahn, who, under the name Dorothy Melendrez, starred as Meryl Stryfe in Trigun.
Quinton Flynn might be recognizable as Axel from Kingdom Hearts 2, Raiden from Metal Gear Solid 2 and 4, and Reno in Final Fantasy VII: Advent Children. He's best friends with Jeff Nimoy, who is well-known for his performance as Nicolas D. Wolfwood in Trigun.