Since Apple made the design decision to forgo glare-free screens on MacBooks, iMacs, and Cinema Displays, a common problem for lots of users is reflection of light off of displays. It seems to be particularly bad if you sit with your back to a window, and it can cause both figurative and literal headaches.
RadTech has come out with some cool products for Macs over the years. For example, I've owned at least one of their ScreenSavrz "LCD Display protection, cleaning, and refinishing systems" for each MacBook I've had. The company is always in touch with the pulse of the Mac community, so it didn't entirely surprise me when they recently started selling ClearCal Anti-Glare films for MacBook, MacBook Pro, 24" iMac, and the 24" Cinema Display.
ClearCal is similar to the films you can get for iPhone and iPod touch screens, but in addition to protecting your screen, it also provides a solution for those pesky reflections. As you can see in the marketing shot to the right, it appears to do a decent job of making your Mac screen anti-glare. You can even remove the ClearCal a few times, wash it, and re-install it.
RadTech has an installation video if you're interested in seeing how easy or difficult it is to apply the ClearCal film to your display. Pricing starts at US$19.95 and peaks at US$25.95 for the 24" iMac and CInema Display. As soon as I replace my old iMac with a new 24", I'm installing a ClearCal so I can see more of my screen and less of the glare from the picture window behind me.