ScreenFloat, now available on the Mac App Store, is a small utility that does one simple thing: float screenshots above all your other windows. Seems silly at first, right? It's not. I've been beta testing this app for over a year, and every time I open it, I'm amazed at how useful this functionality is.
Take, for example, InDesign. There's plenty of data that can't be quickly copied and pasted into a document, and InDesign tends to obscure everything but what you're working on with its interface elements. With ScreenFloat, I just hit Command+Shift+2 and snap a quick shot of the information I need to reference. When I switch back to InDesign, that screenshot is right there, floating wherever I move it to. InDesign stays focused as I enter what I need. It's great for writing, too. Right now I have a snap of the Mac App Store details for ScreenFlow floating next to the TextMate window where I'm writing this up. Price, release date, how to spell developer Matthias Gansrigler's name ... all instantly available for reference without a single Command+Tab.
I could give you a dozen more examples, but I think that if ScreenFloat is going to be of use to you, you've probably already thought of a few times you could live without a bunch of app switching. ScreenFloat also catalogs previous screenshots, and it has "Open In" functionality for sending them to any other application. It's US$7.99 in the Mac App Store, and in this blogger's opinion, it's an essential tool for anyone doing real work on a Mac.
By the way, Eternal Storms Software (Matthias Gansrigler) is also responsible for Flickery, my favorite Flickr browser. If you haven't checked it out, it's on the Mac App Store as well.