I'm sure there are many but in my cold-medicine-addled brain, Hometown Glory by Adele being played in 2x09 of Skins seems to stand out. Here's a link (http://www.youtube.com/watch?v=HL5jDqj6eB8) but it may be hard to appreciate if you're not familiar with the character-arc (and sort of spoilery if you haven't seen the show and ever plan to). Gorgeous song though.

I've only seen the first two seasons/series of Skins but I find they generally handle the music bit very well :)