Can I enable more key combinations for keyboard shortcuts? I'm wondering if there's any way to enable more key combinations to be used for various actions than those we can use through the standing keyboard shortcuts preference page. For instance using left shift+right shift as a keyboard shortcut to change the input language, or using fn+s for grabbing a screenshot, etc.

Perhaps there's some hack I can use, or an external tool, or just some hidden preference?
QuickKeys allows you to record actions or define macros and assign them to keyboard shortcuts. I don't know if the Macintosh draws a distinction between Right Shift and Left Shift though.