Hey C..
First, I'm so jealous that you have a babysitter to help you while you're at home! :o)
Second, check out meetup.com. You can find playgroups through them, and I know there are a few good ones in this area for new mommies, like Kenmore Moms Group or Dragonflies and Ladybugs. You just type in your location information and what kind of group you're looking for (moms group or playgroup, etc.) and it will find anything matching in your area. Most are free and a few cost a minimal amount (like $30/year or $5/month). CafeMom.com also has a similar forum that you can check out. You could also use both or either to start your own group! :o)
Also, there's the MOMS Club, which has chapters all over the US. I used to be apart of the Bothell/Kenmore chapter, which was great. You can check them out at http://www.geocities.com/sunny2190/moms_club.html.
I hope that helps. Good luck!
~W.~