There aren't a lot of rentals in town but I'd check out
craigslist: boston classifieds for jobs, apartments, personals, for sale, services, community, and events, the Boston Globe online, PositiveRelocation.com, and the Dover/Sherborn Hometown Weekly. I don't know if the Dover/Sherborn paper has an online edition but you can contact the paper at
news@hometownweekly.net. Specify which paper you want when you call them, as I think they own several town papers. In the meantime, my sister told me about a 4bd 3.5 ba rental on Page Mill Rd (a pretty neighborhood) with renovated kitchen & baths but it's quite pricey though: $3,850/month.
There is one that's a lot less expensive on Eliot St but it's an antique and likely has lead paint so can't be rented to families with very small childen. I'm not sure what the age restriction is but I'm sure you can Google it. The house is 4bd 2ba being rented for $2,200 and is available immediately. I can send you more details & pictures if you'd like.
I also noticed a colonial home on the corner of Russett Hill Rd and Rt 16 that's for sale by owner. Perhaps they'd consider a rental. I was in that house awhile back and it's beautiful but faces Rt 16 so I bet it will take a while to sell. When I'm out tomorrow I'll get the number for you.
Best of luck!