Grappa

Draw on the blank screen. Pretty!

Easy ways to save what's on your screen:

Windows: Hold down Alt and press printscreen. Open a Word or Paint window (or any word processor or image program). Press ctrl-V to paste the picture into the new window. Save!

Mac: Command-shift-3 (captures screen) (or Cmd-shift-4 to marquee your capture area). Picture file appears on your desktop.

More Mac screen capture tips:
http://discussions.apple.com/thread.jspa?threadID=1191445&tstart=0
http://guides.macrumors.com/Taking_Screenshots_in_Mac_OS_X

Tip: you might have to reload the site after the capture.