I used to use snapzpro and recently switched to iShowU. It is so much better. Where SnapzPro can take 30 minutes to render the video, iShowU takes seconds and it works just as well and is much cheaper. I highly reccomend it. I just posted some screencasts on setting up a google reader account. I used iShowU. You can see them here.
I use IShowU (Mac only). Great tool (independently of price). Tends to produce somewhat big mov files when presentations are more than a few minutes long. You have options, however, to choose different compression/quality options.
I've played with Wink and it doesn't compare with a program like Camtasia. Wink can do some video capture of the desktop, but it doesn't do it very well. What is does well is takes screen shots and allow you to stich them together with a voice over. It will animate the cursor so it appears to be captured video. You can add clickable buttons as well. You can save the whole thing as a flash presentation or a standalone exe. It's worth a look, but is a little limited and there is a bit of a learning curve.
I've used iShowU on my MacBook and I like it. I've only done a few captures, but it's worked like a charm. The cool thing is no matter how long I capture for the video file is available instantly on the desktop, no waiting for it to render.
Teacher Tube has a short video demonstrating how to use CamStudio, a Free program, for screencapturing and making in flash or avi videos. I use a pc, and I am new at this, but did install it and use it to make a video (to demonstrate to a committee how to unpack an encrypted email attachment), and it was pretty cool. Check out the video tutorial at http://www.teachertube.com/
I use camtasia, but I have also just taken screen shots and uploaded them to a site like SplashCastMedia. Quick, easy, free, and best of all, the splashcast player has a selection feature that lets the viewer choose between any of your movies. http://www.splashcastmedia.com/
I discovered another PC resource for capturing video called CamStudio. It's free and not too bad. To test it out I captured a trip down the Grand Canyon in Google Earth. It did far better than I'd expected.