You can catch a regular bus from outside rimimni train station to San Marino. San Marino is a village on top of a mountain with 200 souvenir shops that sell weapons mainly. No wonder the Italians couldn't conquer them!!!
San Leo and Gradara castle.
San Leo is a small pictoresque village, just a few kilometers outside Rimini.
Gradara castle is a castle may be 20/30 minuts far from Rimini, I know that there are excursions in summer, but you can ask to Rimini tourist information office to see how to go in low season.
The small town of Villa Verucchio is located about 10km from Rimini. There a small fine restaurant is found in the center of town called Casa Zanni. I had a wonderful meal in the gardens behind the restaurant (which are not visible from the road) - Piadini cooked over a wood fired stove, home made everything (from olive oil to wine) and fantastic pasta and sausage. They have a web site at http://www.casazanni.it/gb/home.asp (in both english and italian). Drive up to the hill top city first, walk around and look for the small ceramic mosiacs set into the stone walls of the village. Then drive down and visit casa zanni.