Last year I bought Natalie MacMaster's latest CD and loved it. She performed at The Old Town School, but I missed that. Although she's added "modernist" elements to Cape Breton roots music, she stems from the tradition of the Canadian maritimes that still flourishes.
Start with The Cape Breton Fiddlers Association with free MP3 downloads. Then check out Allie Bennett's Links page to see a wide range of traditionalists and modernists. One "modernist" is Jimmy Rankin of the Rankin Family whose latest CD, "Handmade," is quite good. (Sample some tracks here.)
Don't miss out on the Cape Breton Live Radio site. I'm watching a streaming video of Natalie and Buddy (her Dad) MacMaster in a local concert setting. It's superb. Enjoy! Finally, there's an informative, easy-to-read posting about Cape Breton fiddle music on the Wikipedia.