http://www.agriturismomolinuzzo.com/en/

It's been a while, but we loved this place, halfway between Florence and Siena.

As PP mentioned, the area south of Siena is very nice.

Parker Villas is also good

We stayed here - http://www.villainumbria.com/private-villas-in-umbria/overview-of-private-villas-for-rent-in-umbria/la-torre - but it's in Umbria.

Don't know if I could find the exact place we stayed but I recommend looking in the Val D'Orcia (south of Siena) -- very scenic, lots of hill towns to visit and you can do Florence as a day trip if you want.

http://www.dowhatyouloveinitaly.com

We've gone through James twice- both times have been great. Tons of reviews that can help you pick the best house for your family/group.

We are going next spring- and are using VRBO. Book soon. The good ones go fast.

We are thinking of renting a villa for a couple of weeks in Tuscany next summer. Anyone have any recs on a place they stayed and loved?