Tools

Knowclue's pick for MAC :  Real Time Capture

iShowU (basic - what I use with Students) 

IShowU HD (pro) 

Stomp (codec converter)

Other Screen Capture Tools:

Dual Platform:

Jing (free) dual platform 5 min. capture limit

Jing (pro)

Windows 

Fraps

Camtasia

iShowU Settings:

Basic without sound

Basic with sound (make sure "Microphone Input" is set correctly to show device you are using)

Trouble Shooting: