Eaton Chelsea at Yonge and Gerrard - heavy traffic and lower end, relatively, but not too bad
Sheraton Centre at Bay and Queen - my personal favourite in terms of meeting all needs like location, price, quality
Marriott at Bay and Dundas - nice, but can be VERY expensive relative to room
Bond Place at Yonge and Dundas - decent but tiny rooms, need a key card to use elevator so its a no-go for me
Courtyard Marriott at Yonge and Carlton I think - No. 1 in terms of proximity to agencies. There is also a Holiday Inn basically next door that's not worth what they charge but has what you need.
King Edward is very nice, but I'd look for specials online or the price can get out of hand during the warmer months.
Intercontinental at Front and York ( I think) small, clean, reasonable, basically right next to union station and short walk to a whole host of agencies. About ten minute walk to Eaton Centre