Keyboard shortcut to start slide show from current slide
Press F5 in PowerPoint/Windows or Control-Shift-S in PowerPoint X/Mac to start a slide presentation from the beginning
Press Shift+F5 in PowerPoint 2003 or Control+Shift+B in PowerPoint X/Macintosh to start a presentation from the current slide
There's no PowerPoint/Windows keyboard shortcut for this in earlier PowerPoint versions, but you can click the SlideShow icon at the lower left of the PowerPoint window to accomplish the same thing.
Note: none of these shortcuts work in PowerPoint 2001/Mac (but clicking the SlideShow icon works the same)
Download Shortcuts for PowerPoint from OfficeOne, Chirag Dalal's site that includes many other tips, tricks and examples of the features available in Microsoft Office products through VBA.
It enables you to start the slide show from the current slide using a keyboard shortcut.