Not sure if this is the same group that the others have mentioned, you can considering joining this:
http://www.meetup.com/singleparents-519/
They seemed to organize meetups for single parents. Even if you don't meet someone suitable for dating, it is good to get in touch with other single parents and share with one another the challenges. Widening your social circle would definitely help increase the chances of meeting someone.
I agree with joining a club or a class to meet people too. Will be good since you will be in a group with similar interest. Even better since you get to do something you enjoy.
All the best!! :)
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