There is a regular bus service between Rimini and San Marino. The journey takes around one hour.
Buses to San Marino from Rimini start opposite the train station. I bought the ticket from a woman when the bus arrived. I think these are sold also at a booth outside the train station.
If you're going to San Marino by car, you can park in the nearby town of Borgo Maggiore and take the 1.5 km cable car up to San Marino. Otherwise you can park your car in San Marino at one of the car parks, but outside the walled section. They say these car parks are expensive.
We arrived in Rimini and found a small bus office just outside the train station. The staff there spoke a little English and we bought tickets (8 euro) for the trip to San Marino.
There are many busses each day (see photo) and the bus stop is opposite the railway station and well signposted. The trip there is about 35 minutes.
Don't dispair if the weather isn't too good, San Marino is at the top of a mountain (749m above sea level) and on most days is above the clouds with good weather.
Got to San Marino in about 45 mins from Rimini - take the 'Bellini bus' from opposite the train station (low season), as I did - - - or you can apparently go from the beach (Mare) in high-season, too.
Cost = about 3 or 4 euros return, so good value.
A No 17 bus from the train station in Rimini will transport you the 23 km to San Marino. In practice, nobody needs a visa since there are no border checks, and the local authorities take the sensible view that anyone who has satisfied Italian entry requirements can probably be safely allowed into the country. You could try for a visa at one of San Marino's very few embassies around the world or at its Permanent Mission to the UN in New York, just around the corner from old Cliffie's favourite hotel in the Big Apple - now, don't y'all want to run on over to check out my neat New York page!? If they won't give you a visa, you'll just have to do what everyone else does: go to the tourist information office in the main square in San Marino and hand over five euros for the colourful 'transit visa' they'll be happy to stick in your passport.
The easiest and most popular way to get to San Marino is taking the coach from Rimini. It is surely also an interesting alternative for people travelling by car as parking lots are hard to find in the old town of San Marino. A return ticket costs 8,00 EUR (April 2006). The coach runs once an hour during the high season, but less frequently off-season.
The driver was not the friendliest one and didn't allow me to take my backpack (which was really not that large) into the passenger cabin. I had to put it down into the hold and it was almost black when I took it out...
CLICK ON THE SCHEDULE TO SEE THE ENLARGED BUS SCHEDULE.
The easiest way is to take a bus from Rimni. You can stay anywhere in the area and take a train to Rimini. I stayed in bologna, and trains run about every 30 minutes to Rimini from there. Bolgna to Rimini takes 1 hour. the buses from Rimini to San marino run about 9 times per day and it takes 45 minutes. the price roundtrip is just over 6 Euros. The photo is of the bus schedule. Last bus down is at 6:30 PM. Don't miss the last bus as a taxi will costs 40 Euros!