OVERUSED THOUGH. Or at least the first one is.
To OP, try finding something your self on youtube, for example what kind of music are you into? Rock, Trance, pop, drum and bass, dubstep (yuk in mainstream though) etc. Also find something that will fit the video pace as well, if they are short od caps, then use something ubeat, if they are longer speed caps, try something more slow and relaxing. (I.e. Phan's cap videos are a good example where music blends in)
I have good music that I like, and I could use for a capping video when I build my new computer, so therefore I'm not going to share otherwise I'll be accused of stealing the music from another video.