Subordinating conjunctions always seem to raise the most questions for me, specifically in the differences between obwohl and obgleich. The text I am using in my studies states that they both mean "although," but when should I use one over the other? My text is not very clear on this and I'd like some sort of clarification to improve my German usage in the long-run.
For your active knowledge, just forget about "obgleich"; just use "obwohl" all the time – the basic meaning is the same. I actually don't know if I ever used "obgleich" in the spoken language (and I'm a native speaker).
Both words are very similar in meaning, though obgleich may sound slightly more archaic to some. Obwohl seems to be younger. However, Canoo.net lists these as meaning the same, while there are several other similar words that have an elevated connotation, like obzwar, wenngleich, obschon and wiewohl.
I think you hear obwohl more in everyday language, while obgleich is more used in written language.
"Obgleich" is a more archaic and poetic version of the word. You won't hear it used outside of poems these days.