I never use the scroll lock key nor the caps lock key. I just discovered this, which made me think, is there anything else I can do with the leds? Let me know if you have any suggests. (windows only please)
See wiki article on this topic.
Excel uses it (and I think Excel is cool) If you hit scroll lock then move around the sheet using the usual page up / down or arrow keys then you see different parts of the sheet, but the active cell remains unchanged.
This is great when troubleshooting or checking formulas and results, as an easy way to move around your data while still staying in one place, which is then easier to return to (eg press scroll lock again to turn it off, press right arrow , left arrow and Excel will bring the active cell back into the visible window).