Pixel Bender is used for image processing - special effects in programs like Photoshop and After Effects, in fact both of those programs have a menu entry for Pixel Bender filters. In addition to the filters that we ship as built ins, you can write extra filters, drop them into a directory on your hard drive and use those custom filters in PS and AE, and also use those filters in the Flash player.
There are lots of links to information and tutorials on Kevin Goldsmith's blog here:
Lots of cool examples on the Pixel Bender exchange here:
And a development toolkit with documentation that can be downloaded here:
It's hard to say whether Pixel Bender will be useful for you without knowing more about how you use the Creative Suite. The best place for you to start is probably at the Adobe Pixel Bender Technology Center, http://www.adobe.com/devnet/pixelbender.html. You should be able to get a good overview of what Pixel Bender is and how it can benefit you. You might start with the "Effects with the Pixel Bender Toolkit" series by Kevin Goldsmith. You might also try the Pixel Bender plugin for Photoshop CS5 which is not installed as part of the CS5 distributables but can be downloaded from the Adobe Labs, http://labs.adobe.com/technologies/pixelbenderplugin/. Beyond that, a quick google search of "Pixel Bender" should turn up examples of how Creative Suite users are using the Pixel Bender technology. FYI: Pixel Bender support is available in After Effects, Flash, and Photoshop as part of CS5.
This presentation from Russell Brown will also give you a good look into Pixel Bender and one of its uses:
There's also another presentation from Russell Brown about more advanced Pixel Bender techniques:
You can find both presentations (including options for mobile devices) by searching for "Pixel Bender" on Russell's "Tips" page: