During my summer in Salamanca, I have travelled every weekend. It's tiring, but completely worth it. I cannot imagine coming to another country and just sitting around on the weekends. I have seen so much of Spain by getting out there, taking the Renfe, and exploring new places.
Cursos Internacioles offers many excursions for students. I only signed up for one weekend with them, to Lisboa, Portugal. My roommate went to Segovia and Toledo with them as well. They offer great day trips as well as the weekend excursion. Moving on to the fun, travel bits:
Lisboa is beautiful. The capital of Portugal, there is so much to see. Going with the school was a great way to see the city. Everything but food is taken care of (by you, earlier, but still it's not a hassle.) and they offer great tours. Our guide was really nice. Of course, since we have a language program, everything is done in Spanish. We were able to tour a super old castle on the first day of arriving there as well as multiple cathedrals, an old town, a beautiful beach, and metropolitan Lisboa.
Since pictures speak louder than words:
One of the things I loved about Lisboa was how clean everything was, and also how beautiful. The Portugese people make things beautiful just so that they are beautiful. Even the metro stations were decorated intricately. I loved it.
One of the most important parts of any culture is their food. You should always try something at least once, in my opinion.
There were a few people on our trip who seemed to be anti-culture. While the group stopped to get Nata, one girl went into the Starbucks next door to get a coffee and a cookie. Seriously? There are plenty of those in the United States. Other students went back to the hotel and took naps during our freetime instead of exploring the city. My one suggestion about traveling, if you are going to do it, commit, and soak up as much of it as you possibly can.
I think Lisboa was one of my favorite cities out of the five I visited.