Part of the reason the show "Glee" has always appealed to me - even when I feel it's suffered from slumps - is the intrinsic concept of found songs that perfectly encapsulate a moment, a scene, a character. It's a different feel from a true musical, where the songs are written to suit the characters; here, the process is more organic, finding two things that just happen to fit together. It's the joy in discovering a personal facet to something (more or less) universal.
I do this a lot with the music I listen to, and much of it gets permanently associated with a character, a scene or a situation - so much that even years later, if I play a certain song, I get flashbacks. Gloria Estefan's "Dangerous Game" will always conjure memories of Miayde and Treddian from Butterfly's Poison, the character assassin and her scheming opposite; Leann Rimes' "The Safest Place" may have gotten a place in the Scylla and Charybdis soundtrack, but it still rings of its original place describing the (unrequited) romance between Mikane and Tieruko. (Hmm ... what is it with me and M and T couples?)
Unnatural Causes has a songlist, but the associations aren't permanent in my head yet. Probably the snarkiest choice I made, however, was for the queen, a minor character who largely serves to stand as an authority figure in the background.
Her themesong? "What Do The Simple Folk Do?" from Camelot.