Here are a couple of places for Marin Short Term Rentals http://www.mesuites.com/index.html
You might even be able to check with a couple of our local companies such as Fireman's Fund and Autodesk (they both have a lot of contractors in and out of the areas) and see if they will need a short term solution for their employees / contractors.
Another resource is to list it on Craigslist - most of MLS and property management companies in town do not handle short term rentals, but if I was you, I will at least call and try and see if any will help you.
Other option might be to ask your Realtor. We sometimes will receive realtor email asking if any of us have clients who might need a home for a few months.
Just curious, your profile says home selling but you want to rent for three months. Any special reason for doing so? The reason I am asking is if your goal is to sell the house in June, you might want to think about how long or if there will be problem with getting the house ready for sale when there is renter in the house.
Hope this helps.