I normally use Screencast-O-Matic to make screencasts (see the one I made on organizing your bookmarks bar in your Chrome browser, and there’s also a series on working with Google Docs – try this one about how to use voice comments with Google Docs!), but last week I branched out and tried Nimbus.
With Nimbus, you can screenshot (the whole page? a portion of the page? whatever you want!), or you can make a quick screencast…either with sounds or without. I made the screencast from the last entry using Nimbus, just to practice…and it took me about five minutes to figure out.