I would recommend the Michelin map book over any others.

As another poster noted, look for the brown "i" signs in most towns, tourist info offices can book you into local B&Bs. We tried to hit the "i" by about 2:30 or 3 p.m., then you can explore the town with reservation in hand.

I've used Enterprise, Avis, AutoEurope, and a small private company for hire cars. You can comparison-shop online for the lowest price -- we enjoy a small minivan (about 4/5 size of American minivans) because you sit up higher and can see more as you travel.

If you are a Costco member, link to the rental car co through Costco Travel website -- we found a significant savings there, last trip. There are more automatic transmission rentals available now than in years past, but if you can't/don't want to drive a stick shift be sure to specify!

If you are going to be staying in one place for three nights or more, consider a self-catering property. Check Slow Travel for ideas, reviews, links.

And yes, flexibility is the key to having a great time!