In September we are going to Rome, Florence and Tuscany. We like to go biking out into the country and enjoy the scenery. Has anyone had any experience biking in Tuscany? Where are there good places to bike, places to rent bikes etc. We will be staying in San Gimignano and taking day trips out to various places in Tuscany such as Montepulciano, Montacino, Pisa, Siena, Cortona, and other small towns in the area. We also like to take hikes.
Thanks for any help on biking you may give.

I biked through Tuscany in May, and my trip report is posted here (click on my name to find it). I have been in and around Florence, Siena, San Gimignano, Pienza and Montepulciano. I did it on an organized tour though, and it sounds like you want to do it on your own. I don't think I could have come up with the same routes (which were safe as well as extremely scenic) on my own as the tour company did. But I will say that the further south we went, the more dramatic and amazing the scenery got. I highly recommend the areas around Pienza and Montepulciano. Good luck!

Do you have a good map of Tuscany?
If you plan to day trip from San Gim. then you need to alter your plans. Most of the towns you mention may be too far for bike trips on roads that may not be convenient. I suggest you consider 3 destinations from that location--Volterra, Certaldo, and Monteriggioni. These will be feasible.

I'm doing a cycling trip to Tuscany on my own in September. It's a self-guided tour with irondonkey.com They provide the bikes, maps, accommodations and 4 dinners for a very reasonable price. You may want to check it out to get an idea of their itinerary.

Here you can find a list of links about biking in Tuscany: http://www.casinadirosa.it/en/links-bici.html

I know Maremma in Bici and they are great.