This is one of Toronto's finest shopping streets, with boutiques and better known fashion labels. There are also several funky restaurants and second-hand stores as you go further west.
On Queen St, obviously. Although the busiest area is probably the block east of Spadina, many of the more interesting shops and restaurants can be found if you cross Spadina and continue west
Updates
Definitely go west of Spadina for the best of Queen West - look out for Java House (independent coffee shop with great cheap food) and Fressen (incredible vegan restaurant). You could walk west along Queen for days and it'd never stop surprising.
Is this your business?