Adobe Audition (formerly CoolEdit) can do wonders with voice as well as music! You can check out the free trial at:
http://www.adobe.com/products/tryadobe/main.jsp#product=92 I have used it for years, as I was in an acting troup and we used it for all of our voice over effects. There are also tons of fan sites with info on effects, as well as just making your voice overs sound as good as possible.
P.S.- just curious, what kind of game are you making that will need voice overs? Maybe I can help in some way. Maybe cleaning up a rough script or something (I have written plays for the last seven years)?
Fraggles where quite the scary lot...