I think the major churches and Old Montreal and things like Place d'Armes are all pretty obvious and easy to find. One other park is Mount Royal, the outlook on top and the cemeteries (this park designed by the same man who did Central Park in NYC).

You have probably already seen the STM website for public transit... but just in case:
http://www.stm.info

Some of the main museums in Montreal:
http://www.montreal.com/tourism/museums.html

I see the Fairmont Queen Elizabeth in Montreal has some special weekend rates through September 2 ($125)
http://dir.travelzoo.com/Lodging.asp...y=21&id=105826

I have heard and read some good things about the Omni, but have never stayed there. It is sometimes available through Priceline, though.

I loved Montreal, but I also really liked Quebec City (similar to the relationship between Vancouver and Victoria?). It's not a long way to Quebec City and there is some pretty scenery along the way. I would strongly recommend spending a bit of time outside of the major city, but that might be just a personal preference.