Clarify for Mac and Windows
Clarify looks like a great way to organize and prepare screenshots for tutorials and walk throughs - something I'm often doing with clients.
At $29.99 in the Mac App Store it's not something that's going to replace the simple Command-Shift-3 screenshot utility built into OS X for most people - but if it's something you're doing a lot throughout the day, this will save you a bunch of time. Plus the built in Dropbox sharing makes it easy to send out to clients who might not have a large email attachment option.
Clarify is also available for Windows XP, Vista or Windows 7.
Here's my quick sample screenshots created with Clarify. Riveting.