"Quick way to zoom on Photoshop"
If you're working on something and need to zoom in on an area to edit or just inspect it, you can hold Ctrl+Spacebar and then click and drag the box over the area you want to zoom in on. This doesn't matter what tool you're in. To zoom all the way back out to full screen, click Ctrl+0 (thats a zero). This has saved me a lot of time editing.
This is on a PC.
And yes, it does work this way in CS5, you have to turn off Scrubby Zoom first.
To do this, click on the Zoom Tool in your Tools Palette a then uncheck Scrubby Zoom in the bar on the top of the window."