To my knowledge, I couldn't find any hotels that are outside of Toronto - that is along the Lakeshore West train line - but all I know that there is a Super 8 Hotel in Ajax, which is south of the Ajax GO station, but it's within walking distance. Information for that hotel can be founded here: http://www.super8.com/Super8/control/Booking/property_info?propertyId=13920
As for hotels in downtown Toronto, the only hotels that I know out of my head are:
- Westin Harbour Castle Toronto (http://www.starwoodhotels.com/westin/property/overview/index.html?propertyID=1084 - this hotel is overlooking Lake Ontario)
- Fairmont Royal York Hotel (its located outside of Union Station)
these two hotels are conveniently located near Exhibition Place, but they are within distance by public transit. Further more hotels can be founded here:
http://www.expedia.ca/Exhibition-Place-Hotels.0-l6072455-0.Travel-Guide-Filter-Hotels
It's also even cheaper if you book through the following websites:
http://www.hotwire.com
http://www.priceline.com
http://www.expedia.ca
http://www.hotels.ca
http://www.travelocity.ca
Based on your recent comment, there's some hotels near the Oakville GO station:
1) Holiday Inn Hotel Oakville Centre:
590 Argus Road, Oakville, Ontario.
Telephone:+1-905-842-5000 or toll-free at 1-877-660-8550.
That hotel is located near the Oakville GO station - but within walking distance.
Source: http://www.holidayinn.com/hotels/us/en/oakville/yyzok/hoteldetail
2) Monty Carlo Inn Oakville East:
374 South Service Road, Oakville, Ontario.
Telephone: +1-905-849-9500 or toll-free at 1-877-849-9500
This hotel is also within walking distance from the Oakville GO station. Full information can be founded here:
http://www.montecarloinns.com/oakvillesuites.html?reloaded=true
As for Mississauga, all I can find is some hotels/inns near the Port Credit GO Station:
1) Ports Hotel located at 30 Port Street east, Mississauga, Ontario:
http://www.portshotel.ca/
Telephone number: +1-905-274-7390
2) The Waterside inn located at 15 Stavebank Road South, Mississauga, Ontario:
http://www.watersideinn.ca/
Telephone number: +1-905-891-7770 or toll-free at 1-877-264-7770.
Both of these hotels are located near the Port Credit GO station - within walking distance. I hope the updated information clarifies you.
If you prefer, Travelocity offers a special promotion called "Top Secret Hotels" - in which you can save up to 45% off on top hotels. The hotel name will only be revealed - after you book online. Information can be founded here:
http://leisure.travelocity.ca/Promotions/0,,TCYCA|5301|hotels_main,00.html?locLink=SOHP7&WA1=03030&WA2=FDhotel&WA3=455&WA4=100318_top_secret_455jpg&WA5=IM&WA7=96
I hope this helps.