QUOTE
My teacher calls the bowing over the fingerboard, flautando (not sure on the spelling!), which is played with fast long bows, creating a very quiet whispery sound, very good for producing a contrast in dynamics and tone. I used it in two of my grade 8 pieces.
This is correct, although flautando is slightly different to sul tasto. Flautando is basically a more extreme version, with a very fast light bow movement, whereas sul tasto is more to do with just the positioning of the bow on the string as opposed to the stroke. In other words, sul tasto is used more for dynamic,and flautando is more for effect (although both have a bit of both!)
Sorry if that post didn't make much sense, I'm not very good with words...