Though more known for pairs (obviously), Jamie Sale and David Pelletier both competed in singles and had some success.
David was 4th at the 1995 Canadians (2nd in the SP!!) in senior mens, and Jamie was 5th in senior ladies the same year (3rd in junior the year before) and was 12th at junior worlds that year. She also came 6th in 1998.
IIRC, didn't Kurt Browning dabble in pairs a bit in his free time? Maybe back when he was training alongside Kristi Yamaguchi?
And as I mentioned in the Fedor/Jana thread, Fedor and Jenny Kirk tried pairs for a while, though his back troubles (and, I'm assuming, citizenship issues with the two) caused the end of that.