It's a little tricky to do it with Flash, but it can be done. It would, however, require some server side support. With the many advancements in Flash it's now possible to create a bitmap image within flash, render a flash drawing to that and then capture the bitmap data. You could then send that data to an external script which could re-render that bitmap data into an image for saving or viewing on a web browser. There are other techniques out there to compress the data (which is essentially a raw bitmap, so you can imagine how big those can get) so that it saves on bandwith.
Here's just one solution:
http://sephiroth.it/tutorials/flashPHP/print_screen/
Steven