CasterSoundboard - A soundboard for hot-keying and playing back sounds. (For podcasting)
EarTrumpet - Volume Control for Windows
Soundpad - Play sounds in voice chats in high digital quality.
Sound Control - App-specific volume control
Soundboard Studio - Soundboard Studio lets you take your podcast, live show, gig or performance to the next level.
Power mixer - Power Mixer is a complete Windows volume control replacement.