[QUOTE=blackjack-21]jen,
The airport limosines are right outside the terminals, and are usually in a different lineup then the taxis, shuttle buses. Careful, because some are actually taxis, and will charge by the meter. The real airport limos (usually Caddys or Lincoln Towncars) charge you a zone fare (flat rate) depending on your destination, and you should inquire when you get in the car, what the fare will be. ]
Blackjack-21 and jen:
I realize this is a month-old thread (so jen might not be following it anymore), but I'm not sure Blackjack-21's answer is completely correct.
At the airport, there are easy-to-find lines outside the arrivals area for "limos" and "taxis". Both are served by town cars (the regular metered taxis aren't allowed to pick people up in this area). You'll get charged a flat rate if you take a car from either the taxi or limo line-up, but you'll get charged about $10 more if you pick up one from the limo line-up. I have no idea why. (I've only taken a limo a few times - by accident or because there was a long line of people in the taxi line with no taxis and no one in the limo line-up). Stand in the taxi line-up, wait for a town car (probably no more than a few minutes' wait) and ask them the fare when you get in. It should be in the range of $40-45. They take credit cards, but there are a few bank machines in the public part of the arrivals hall.
When you leave to go back to the airport, call Maple Leaf Taxi (a regular metered taxi service, but generally the most clean and professional of the bunch IMO) at 416 465 5555. Ask the dispatcher to quote you a flat rate to go to the airport. It should be in the range of $30-40 (I'm not sure exactly what zone the Sheraton is in; I used to pay about $34 from a spot a little further north, but I think the rates might have increased a little in the last few months). You can order a car service for pick-up, but Maple Leaf is decent and probably $10-15 cheaper.
And be sure to visit the Bata Shoe Museum at Bloor and St George. A fun, interesting museum where they have done some serious scholarship about footwear, culture and society (the exhibits on aboriginal footwear, footbinding, etc are fascinating). And, of course, they have a great gift shop.