It's interesting that while there are many very excellent whistle players in irish traditional music, there aren't many who are known as whistle players. The only American one that springs to mind at the moment is Kathleen Conneely (besides the obvious Joannie Madden). There are of course the obvious Irish ones, Mary Bergin and Sean Ryan. But every other whistle player I can think of (including Joannie) plays another instrument, often flute. I know it's often true in Ireland, and it is also true here, that people often start on whistle before moving to other things. My fiancee is a fantastic whistle player, as is her brother, but they're both much better known for fiddle and box respectively. But you'd be hard pressed to find better whistle players...
Another thought: after attending Gay McKoen's lecture at the CIAW about Uilleann Pipe clubs, I was talking about how and why there aren't Irish Fiddle clubs, Irish Flute clubs, Irish Whistle clubs, etc. The flute one especially is a bit interesting. Flute is a lot more similar to pipes in that there aren't a ton of makers, the instrument isn't available in stores (and definitely no Flute Shops like there are Violin Shops), and wooden flute players are pretty few and far. Good luck with this, it's an interesting idea, sort of a whistle-tionol. It will be interesting to see how it gets on.