Check out the childcare providers network and look into their childcare connection meetings where parents needing care and caregivers with spaces can meet up and they are free. www.ccprn.com
Worth the $25 yearly membership for the resources they offer. This website daycarebear has been great. Other places to advertise are www.usedottawa.com - look under services - childcare. Also list at www.kijiji.ca. Make sure Ottawa is selected as the city and then list under services - childcare. I live in the east end in Orleans.