You can check Cafe Mom and Joining Moms and try doing a search by location. There are probably some groups for your area there. If there aren't any groups, both of those sites allow you to send messages to members (on that site, so you aren't giving or getting private contact info) where you could send an invite to become friends on the site. Once you're comfortable, pick a public place and meet in person and let things develop from there.
Check local churches for MOPS groups. Local libraries frequently offer age-specific classes for free. You could meet other moms there. Join a co-operative preschool. You'll meet the other moms and can start playdates on off days. If you're out somewhere and see a group of moms that is out together, ask them if it's a mom's group and check into membership.
Some other sites that help you find playgroups and other moms are:
http://orion.lib.mi.us/momsclub/Activities.htm
http://www.meetup.com/
http://www.childavenue.com/pages/playgroups_pages/playgro...
http://www.matchingmoms.org/
http://forums.michiganmoms.com/viewforum.php?f=6
http://www.mommyandme.com/
http://www.motorcitymoms.com/apps/pbcs.dll/section?catego...
http://www.playgroupsusa.com/
Have fun searching :-)