Online Music: What's That Song?

Various ways to identify songs. You can sing, whistle, play their online piano, tap the rhythm, or even say whether the notes go up or down (without knowing the actual notes).

Tap the melody of the song and discover its name

Listens to the music from the radio or you singing/humming and identifies it.
Apps for Apple and Android.

Sing or hum the song and it will identify it.
(Web browser version of SoundHound)

Freeware you can download for Mac or Windows. Requires an Internet connection to identify the song.

Apps for almost any mobile device. Identifies music by listening. Allows you to tag songs. Free and pay versions available.

Search IMSLP/Petrucci for tunes and chords