Mom and Tot Excersize Class...

Sweet Pea Yoga Studio and Bloom Yoga offer a lot of mom and child classes. Both are on the northside.

I go to Stoller Strides. Its a stroller based (obviously) class with walking/jogging, muscle training, etc. They also organize a mom's night out, family night out and play groups. They may not be in your area, but they are in several of the Chicago suburbs. Their website is www.strollerstrides.com. Also, check out your local YMCA or Park District. I also do a yoga class with baby.

I know some hospitals offer a mommy-n-me yoga class. I didn't take it as it was only offered on Saturdays and I wanted something during the week. There are Kindermusik classes offered at most park districts which incorporate some exercise, but it's not an exercise class, per se.

E.,
For yoga classes, check out the offerings at the Oak Park YMCA, the Oak Park Park District, and the River Forest Community Center. I'll bet at least one of these places will have something that interests you.
Amy