Creative's Liveware that comes with the SB Live cards can change the sound (from anything, like an MP3 or in your case, a microphone) in real-time.
Liveware 3.0 comes with lots of effects you can apply to your mic, like Pitch Shift (male to female effect or vice versa) and 'alien', 'chipmunk', 'underwater' or god-like 'Zeus' effects, which are all combinations of reverb, distortion, chorus, auto-wah etc. etc.... Quite fun to play with and fully customizable
I haven't actually done any recording of this, but the effects should transfer just fine from microphone (or in my case, electric guitar hooked into the mic plug) and onto a .wav file....