The most interesting aspect of my geocaching has been an almost obsessive increase in my interest of learning more about local Nevada history. I've lived in my home town for over 45 years, but it wasn't until I started caching almost 4 years ago that I learned the California Emigrant Trail and Transcontinental Railroad practically ran through our town...in fact, portions of both run onto the property of the company I work for, and nobody knew it! My junior high school Nevada history teacher never mentioned it in her class (she probably didn't know either). This has lead to my involvement with the local chapter of the OCTA, volunteering to help do trail cleanups every year.
I've learned about the Transcontinental Airmail route because I logged a benchmark off the GC.com website, and wondered what the lighted tower I'd benchmarked was used for. I've learned about an almost forgotten wagon freight road that operated for ten years between Wadsworth and Columbus that I (nor anybody I know) had ever heard of...all because of geocaching.
It's almost been like going back to school, only more fun!