I just clipped each individual frame of one of my toonlets and put them in an open office presentation. Then I fired up Berio and ran the slideshow fullscreen while I read the lines. Then I imported the whole thing into IMovie, clipped the beginning and end, compressed it a little and uploaded it to Youtube.
Have you seen http://www.xtranormal.com/ ? It doesn’t have the cool characters of Toonlet but it kind of does this stuff on the fly.