We found a scenic drive through the hill towns of Tuscany in the Fodors Italy book. It begins in Siena and makes stops at Abbzzia Di monte Oliveto M aggiore, Museo d'Arte Sacra, Âontalcino, Sant Antimo, Bagno ?igoni, san Quirico, Pienza , Montepolciano and san Gimingano
Is this too many stops for a day trip? If so, which are the better places to stop? Is there a bus tour that makes a similar trip?

Yes, way too much for a day trip. Remember these are two lane country roads with slow moving vehicles. When you get to a town you have to find a parking place, find a ticket machine, figure it out, walk usually up to the town and then look around, maybe eat or drink, then back down to the car and do it all again.

I would not recommend rushing around and nothing is fast in Tuscany, except the Autostrada.

This would have to be a long one-day drive in which you really don't stop at more than one or two villages. As SeaUrchin said, you'd never get through the itinerary if you stopped and explored every town. However, I think part of the reason Fodor's suggested this route is that it's just a pleasant drive through some enchanting and scenic countryside. If you want to see lots of countryside and a few towns, then it's certainly possible in a day. Good luck.

Oh yes, that is really really too much for one single day!
Monte oLiveto Maggiore would require half a day on its own!
The same goes for the other places.
We went to Tuscany (Civitella Marittima at Casina di Rosa http://www.casinadirosa.it/) and we drove along the road you mention. We stopped in Sant'Antimo, then we went to Montalcino and then Pienza and it was TIRING! San Gimignano is totally somewhere else, I think, and Montepulciano, isn't it far too?

Well, anyway, that is really too much. You can feel a whole week with that program!

I have planned out dozens of day trip routes in Tuscany and see this one as a good start--given 3 days. Add Volterra to San Gim. and give yourself 3 days and it will work. From Siena, take the route via Asciano as you head south to the Abbey.