I'll keep adding as I find them...
Groove Room (Kipling, north of Lake shore): weekday before 6 pm $40/3 hours after 6:00pm $40/2hours or $65/4 hours, weekends $50/4 hours. Additional Hour is $15
DC Music (Kipling, south of Bloor): small room (up to 5) and medium (up to 10) for $15 / 20 per hour (less on weekdays).
amusikzone (Broadview station): various rehearsal rooms, can rent keyboard, $50-60 for 3 hours.
Rehearsal Factory: hourly rehearsal rooms, no prices posted
Bluewater Studios (Bloor and Lansdowne) has a piano but no prices listed (sounds professional though
Music Rehearsal Toronto (Elm / McCaul) -$20/hour, $75 special 6 - 11 pm,
Best Deal in Town (Cherry, south of Gardiner): $17 / hour
there is many more at NOW magazine, craigslist etc. I have a feeling a deposit may be required so I can contact a couple and find out.