This might help a little
http://www.seetorontonow.com/
But my suggestions (along with other people's)
-Ontario Science Center (it's not just for geeks and nerds)
-CN Tower
-Toronto Zoo
-Silver Snail
-Canada's Wonderland
-Royal Ontario Museum (ROM)
-Playdium (if you want to spend a lot of money)
-Art Gallery of Ontario (AGO)
-Hockey Hall of Fame
-Casa Loma
-St. Lawrence Market Complex
-Eaton Center (and that area)
-Ontario Place