You should definitely go to www.meetup.com. You select your interests (moms, breastfeeding, etc.) and then meetup groups that fit your criteria are suggested for you. There are a variety of mom ones, and my friend is in charge of an "Infant Playgroup." Through the site, you can find a variety of things to attend or host your own event. For example, you could offer to host a small playdate through the Infant Playgroup. Or the Stay-At-Home-Mom one has tons of different things going on (and you could join even though you'll be returning to work).
I also go to La Leche League meetings, and to the free stuff at Be By Baby. Both have been a really good support network for me.
My son is now 7 months old, but I built up a network of moms essentially from scratch using those tools! Good luck.