I'm planning a 2 week trip to Spain in October - flying into BCN and out of Madrid. My thought right now is to base myself for a week in each city, and make some day trips from there. I know there are many options for good day (train) trips from Madrid, but what about from Barcelona? Girona? Monserrat? I'm traveling solo and do not want to rent a car.
Montserrat is good: spectacular mountain scenery, the monastery church and some surprisingly secular art works in the gallery. Get a train from Placa de Espanya station and then a cable car or cog railway connection depending on how comfortable you are with heights. The other big cultural day trip is Figueres for the Dali museum if you like surrealist art. Sitges is meant to be fun if you like beach resorts.
We used Barcelona Day Tours company. They provided semiprivate tours on minibuses for not a lot of money. It was 4 years ago. Check them on their web and see what they have. We were very happy with them.
I echo the suggestion for Barcelona Day Tours; we did a half day city tour, Montserrat and Girona/Costa Brava with them in 2008 and were very pleased. Website is www.barcelonadaytours.com.
One city you must visit, so close of Barcelona is Tarragona. It has a great Roman Museum, the city is fantastic, and a 30 minutes by car is Priorat, a great wine county (One, with La Rioja best in Spain) Catalunya is fantastic. In Tarragona I recomend you the restaurant in front of the Roman Forum Good Trip...