Couple of years ago we rented a villa in Italy from http://www.villas.com/

It was a in small village near Florence, cant find it right now, but try searching this website. Make sure to check you need a villa, not apartment, etc

My mother in law rents out her villa in Tuscany.
Website is www.casazia.co.uk
It's beautiful - 4 bedrooms, all en suite, with a big infinity pool (and lots of inflatables for children to play with) set in about 13 acres of pasture and olive groves
There are travel cots and highchairs for guests to use - I think there's even a pushchair
We just got home from a week there with our 6,3 and 1 year old and it's really wonderful

We're looking to rent a villa in Tuscany for the month of September. We're going with our 9month old so we need a baby friendly villa, ideally all on one level or with very few stairs. Minimum 3 bedrooms, with a pool and not too far from local amenities.
If you know of a suitable villa to rent in Tuscany, I would love to hear from you.