I've been using the Qarbon ViewletBuilder for online tutorials for a couple of years now and have been very pleased with it. At a recent meeting a colleague mentioned a freeware alternative called Wink that does pretty much the same thing, so I thought I'd give it a go for comparison's sake.
In a nutshell both of these products allow you to take a series of screenshots, annotate them, and then output them as small Flash files for viewing online. I've been using them as "point-of-use" instructional opportunities, keeping them down to about 2-3 minutes each.
While Wink does indeed get you to a Flash output, I found in my brief trial that it's not as simple to use as ViewletBuilder, nor is the output as nice, IMHO. ViewletBuilder is almost all WYSIWYG, while Wink seems more at the object-oriented stage. Didn't take me very long to sort it out, but it's obviously not as polished as the commercial project.
Having said that though, of course Wink is free, and ViewletBuilder is not, though if your campus buys in bulk it can get pretty resonable.
Here's a quick tutorial I threw together using Wink: How to renew your books (you may have to scroll to see the "next" button in the lower right corner)
Here's the same one done using ViewletBuilder: How to renew your books
With more experience I could probably get the Wink presentation to look a little better (not sure what caused that corruption on the last screen), but I do believe I'll be sticking with ViewletBuilder. Check out Wink if you have no budget though, and I'm sure it'll get the job done.
PS, ViewletBuilder also supports audio (voiceover), a fair amount of interactivity, and the ability to insert simple quizzes. There are a number of other neat products on the Qarbon site, and I have no affiliation with them other than as a happy user.
