Musipedia...when you really want that tune in your head! From the website:

Welcome to Musipedia! Inspired by, but not affiliated with Wikipedia, we are building a searchable, editable, and expandable collection of tunes, melodies, and musical themes.

Every entry can be edited by anybody. An entry can contain a bit of sheet music, a MIDI file, textual information about the work and the composer, and last but not least the Parsons Code, a rough description of the melodic contour, to make the encyclopedia searchable by melody.

Musipedia uses the "Melodyhound" melody search engine. You can find and identify a tune even if the melody is all you know. You can play it on a piano keyboard, whistle or sing it to the computer, or directly use the Parsons code. To "name that tune", you don't need to know the key signature, exact rhythm, or intervals.