Try this first as this seems to have the best results:
A free little program called Tunatic for PC and Mac that I found, that works great just using your laptops internal mic:
Audiotag is nice as you don't need to download any program. On this site it's real simple and pretty self-explanatory. But it basically scans the audio in the provided link or file and compares that to its database. It certainly won't identify all songs but it has helped me to identify a good amount so far. Unfortunately the site is less reliable than it used to be as Youtube links use to work great but now they no longer work, the developer told me Youtube has not allowed his site to scan the audio, bummer. However there is a work-around you can download the flash .flv and then upload it as an attached file, it's a pain in the butt, but it has worked well for me before. But truthfully a better bet is use the app above or the alternative DJCM mentions below.
Good luck and happy digging.
Shazam is a mobile based app that also helps recognize tracks for you.
Midomi is a internet based recognizer where you can sing in to your pc's mic