I think you want Jing. Haven't used it myself, but my understanding is that you can capture anything that you have on your screen to make little video (plus audio) clips.
I will check it out .. but I am really looking for something that I could use "live" while I am explaining something to a student on-line rather than (re-)playing a recording. In class I can use a smartboard and circle various items, or distribute handouts with annotations. (I suppose I could scan these too and then upload it, but that would be too labor intensive, hence my question).
thanks.