Maybe only for the Brit-centric geeks – but the BBC have a somewhat splendid flash app which lets you play with samples from the original Doctor Who theme.
The original and best was composed by Ron Grainger of the BBC Radiophonic Workshop – it’s a classic of early electronic music that even receives homage on Ishkurs (ever updated) Guide.
That is an awesome Doctor Who sound board ! Oops, I just exposed my uber-geekness.