I'm looking at more IMDB entries, this time for the cast of Lost, when I discover that Daniel Dae Kim (Jin) does the voice for Metron in the Justice League series. That totally blows my mind, since I think I remember shitting my pants when Metron made his appearance on the show.
Also Morena Baccarin from Firefly/Serenity and the upcoming Star Trek movie did the voice for Black Canary.
J.K. Simmons who has been in a whole bunch of notable stuff, but most importantly played J. Jonah Jameson in the Spiderman films, does the voice for General Eidling.
Eric Roberts, most recently of Heroes was Mongul.
And finally, Jeremy Pivens as the motherfucking Elongated Man?!?!?!
On another note, I was already aware of this (since, as you can see, I spend so much time wasted on the IMDB), but I thought it was mentionable since Gilmore Girls just ended its 7 year run on television this week. Scott Patterson (Luke) did the voice for King Faraday. His performance as Faraday was so spot on, it brought to mind the term "perfect casting".