Toronto - great modern city by the lake
I worked in Toronto for several months and the only drawback is it is incredibly expensive to live in the city, the only exception (coming from an English person) being the public transport system which was great, and cheap ($3, unlimited transfers). But as a visitor it is a fantastic place to explore, there's something for everyone - whether you want to relax, adventure or shop. And the people are as friendly and polite as they come! Not a great deal of history obviously, but still lots of fun
Insider Tip:Kensington market - for you boho hippies and rockers alike! :)
St Lawrence market - great food, cheaper than supermarkets
Queen Street - for the hipsters out there!
The islands - spend at least a full day exploring and relaxing on the beach
The Red Room on Spadina was by far my favourite bar&food place
If you're staying a while on a small budget, No Frills supermarkets are the cheapest around. Loblaws are a little more, but lovely. I'd avoid Shoppers Drugmart unless you have money to burn!