"Fine and Dandy", a song recorded by Barbra Streisand in 1964 from a 1930's musical of the same name, is a rhythmical and upbeat tune for a tap routine.
Putting on the Ritz has a nice tempo for tapping and the way it is set up you can even break it up for individual dances during the song. It tends to be easier to find then a lot of older songs as well.
You could try "Sisters" or "All I Need is The Girl" from Gypsy. Also "Show off" or "Cold Feets" from Drowsy Chaperone. Any broadway show with tap dancing!