Spend no more than $100 to equip your iSight-less Mac with a web cam, mic, and software necessary to do screen, audio and video capture. Oh, and make it easy.
Mission accomplished for $89.99. Now I can use iChat AV on my MacPro (and Mac Mini), capture full screen full motion video, system audio, audio from other apps, and mic input. Check out the results in this 4.6 MB screen capture scaled to 75%.