What was the name of the song they played at the end of Castle this week?
I actually like Castle*, but hadn't seen the episode yet because I watch it online instead of on television. So, the first step was to get the name of the episode by looking up Castle on Hulu.com ("Wrapped up in Death" aired on 4/5).
Next we searched the internet for "Wrapped up in Death" castle song to see if anyone else was talking about this song. One of the results, heardontv.com, was exactly what we needed - it even described the scene when the song was played. According to that website, the song was "Love Is Endless" by Mozella.
The final step was to search for this song on YouTube just to make sure it was the right one. It was, so the patron was happy.
A video of the song is below, but I warn you: it's catchy, and will likely get stuck in your head. I noticed the patron was humming it when he left twenty minutes later.
*And it humors me to no end that my library actually shelves Richard Castle books.