What are you into specifically though? It'd be easier to give an answer, but this is some vague touristy stuff I did when my cousin was visiting recently:
I'd suggest you check out for sure:
AGO, ROM (both museums), Yorkdale Mall, Kensington Market, Queen West (after Bathurst Street), Eaton Centre, Harbourfront, head to the Toronto island (great for picnics or bike rides), St Lawrence Market (weekends for outdoor vintage shopping), Chinatown (just because), Ripley's Aquarium (a bit overrated but not that bad for one time see), etc.
Restaurants I'd suggest (but depends on your taste): Momofoku is a good spot downtown - rated best restaurant in TO last year, DT Bistro (or anything in the Harbord/Brunswick area, which is in the annex) - great food but better for desserts and shyt, Little Italy (College Street West) has a lot of great spots for food and drinks, Terroni on Queen West is a great restaurant,
For comedy shows/plays/etc, I always check out NOW mag's nightly and weekly listings. Let's you know about a lot of interesting events/galleries, etc taking place + the price range:
http://www.nowtoronto.com/news/listings/