I play relatively frequently for step dancers- so I have tune suggestions and some corrections about information posted above.
The last post is correct- treble jigs are the same thing as a "double jig"- (e.g. Kesh Jig, Swallowtail etc) but danced at a slower tempo. Jigs danced in light shoes are referred to by step dancers as "light jigs" and played at about 116 beats per minute.
Treble jigs are danced at two tempos: 86-92 bpm for "traditional speed" (beginner, and some novice dancers) and 73 bpm for more advanced dancers (novice and higher in competition).
If you are playing for less advanced dancers at the 86-92 bpm speed, some easy jigs are Tobin's Favorite, Connaughtman's Rambles or Irishman's Heart to the Ladies. If you are at the slower tempo, Irishman's Heart still works pretty well...
I heartily recommend that you practice with a metronome and use it when you are playing with the dancers. Melody is less important than keeping a steady rhythm, especially with younger, relatively inexperienced dancers who may be unable to adjust if you vary the tempo(unintentionally of course) ;-) Also, try to get a confirmation on the tempo from the dance teacher. Steps choreographed for a slow treble jig won't work at the faster speed and vice versa
Irish step dance lingo is confusing to musicians- I wrote an entire article on this for a now defunct magazine for Irish dancers- The article entitled "What's a Light Jig?".
To recap: dancer says: light jig musician plays: jig or double jig at 116 bpm
dancer says: double jig or treble jig musician says: that's slow! and plays at 92 or 73 as directed
dancer says: single jig Donal Lunny adlibs: quadruple jig (I love it!)
musician plays: single jig or slide at about 116 (that would be like Off She Goes, Smash the Windows or O'Keefe's slide)
If you're not sure how to differentiate them: *double jigs go "pineapple, pineapple" while single jigs go "humpty-dumpty" in rhythm
dancer says: slip jig musician plays: slip jig (9/8 time) Like Drops of Brandy, Foxhunters, the Butterfly, Dever the Dancer etc.
dancer says: reel (and dances in light shoes) musician plays: reel at 113-120 bpm depending on level of dancer and if it is solo or a figure dance- advanced dancers go slower than beginners or figure dances
dancer says: treble reel and dances in hard shoes musician plays: reel (not as slow as 113)
Any more questions?
Sharon (fiddle, dance-mom)