Pre-school Open Gym at the Dublin Rec Center. Almost every Monday and Friday, from 9-11 a.m., they fill the gym with gazillions of toys and mats and puzzles and the little ones can go crazy (although my son just likes to play at the kitchen set). It costs $3 a visit (you don't have to be a member or even a Dublin resident), but it's totally worth it to me to get out of the house, chit chat with other mommies and have a great napper afterwards.
Also, the swimming lessons at the rec center are fantastic too.
Re: I highly recommend...
I don't know if it's for the summer - I don't think so, though. Probably just when the weather isn't so great and kids can't run around outside.
Your 1 year old will love it! I started taking my son in September, when he was about 10 months and he went nuts just being able to crawl in such a big open space. Now he loves running around, going down the slide, playing in the kitchen. It's such a blast for them.