The main reason people come to Selçuk is to visit nearby Ephesus (Efes). This is one of the largest and most popular archeological sites in Turkey, and can get crowded in summer. Even in late September the crowds were fairly thick.
Many Christian groups tour the area, retracing the footsteps of Paul ("Letters to the Ephesians"). When we went down to breakfast in the Hotel Kale Han on a Tuesday morning we encountered a German group engaged in a private worship service.
You have a tough choice here. The site is confusing without a tour guide (the Lonely Planet book recommends you start at the top but then describes the site working up from the bottom--and none too clearly); and a tour guide will want to hurry you through this huge site faster than you may wish to go. We took our time and managed to figure out most of the sights. We talked with other tourists and eavesdropped on tour guides lecturing in English, French, German, Spanish, and Italian. It's bad form to attach yourself to a tour you haven't paid for; but occasionally listening in while they're sharing the space is almost unavoidable. If we had known how complicated the site was we would have purchased a book at the entrance.
Here we saw heavily laden pomegranate trees among the ruins. At the exit, we enjoyed fresh-squeezed pomegranate-orange drinks. Incidentally, Efes beer is the most popular brand in Turkey, advertised everywhere.