Seconds add up to minutes, minutes add up to hours, and hours add up to days. How much time can be saved by using shortcuts keys? Not sure, do the math. Lots of littles add up to a big. Anyway, I know it may take a little time to learn the shortcut keys but it is well worth it.  Here is a list of links to specific programs shortcut keys.  One question, what are you going to do with all the time you saved?

Browsers
Internet Explorer
Opera
Mozilla Firefox

Operating Systems
Windows XP
Windows Vista
Mac OS X

Software
MS Excel shortcut and function keys,  MS Excel keyboard shortcuts
MS Word shortcut keys1,  MS Word shortcut keys 2
MS PowerPoint 2003, MS PowerPoint 2007,  MS PowerPoint
Adobe Reader 1, Adobe Reader 2