Now for something esoteric…
I grew up in the Orthodox Church. Every Sunday, services were conducted almost exclusively in Church Slavonic, the traditional liturgical language of Slavic Orthodox Churches. Slavonic is the equivalent of Latin in the Roman Catholic Church. While the services in Slavonic can be very beautiful, I had no idea what was being said/sung (there is lots of singing in the Orthodox Church).
After many years away from the Church, I returned in the mid-1990s for about ten years (hah, hah, there’s my ten-year attention span again!). During that time, I attended several churches (even a monastery) and finally began understanding the services. I even went on a pilgrimage to Mount Athos, Greece, considered one of the holiest places on the planet.
Early in my return, I developed a computer-based program to help those interested in learning a few common prayers in Slavonic. The Church Slavonic Etutor was born. The program is no longer supported, and the website is old-school HTML. Most of the site is still functional, with audio files available for those interested in hearing Slavonic and even learning a few prayers. Check it out