There's a lot of offerings around the Hartford area, but none really in Hartford. If you are east of the river you may want to look into the coop in Manchester that runs out of the Lutz Children's Museum. I'm pretty sure they offer classes for younger kids. I'm west of the river and we participate in a few different things, but no formal coops right now. There are a few though, we did the Greenspring Coop in Middletown last year and enjoyed it. They only offer a few classes for the younger ("preschool") crowd though.
There's a good email group on Yahoo for all of CT... if you aren't already on it, you may want to join:
http://www.groups.yahoo.com/group/CTHomeschoolersInclusive
Hope that helps!