We will be in Barcelona in late September for a meeting. We plan to take an ATG walking tour, the Hills of Girona, a few days after the end of the meeting. We have about three days to rent a car and tool around or take a train somewhere and tool around. Any suggestions?

you can tour the cava (spanish champagne region) at Sant-Sadurni d'Anoia and Villafranca del Penédes. or you can go to the French border (many lovely towns along the way) and visit Banyuls, Collioure.

I have a couple friends who are visiting in southern Barcelona right now, and they asked me to inquire what kinds of things there are to do in the area. They've already visited the Sagrada Familia and Parc Guell, and They're not really interested in any day trips out of the area, as they only have a few more days there. They'd rather focus on exploring Barcelona itself.

Anyone have any ideas?

I thought about creating a separate thread, but this seemed to be pretty much along the same lines, and I didn't see the need to create an unnecessary duplicate.

I haven't gotten to barcelona yet, but on my list in addition to all the gaudi sights are:

The National Art Museum

The Maritime Museum

a chocolate museum

and the Barcelona Shoe museum

The Maritime Museum is excellent and an interesting thing to do for 2 - 3 hours.

Casa Batllo' (Passeg de Gracia), another of Gaudi's works, is outstanding. A bit costly at 16 euro entrance fee, but that does include the audio visual guide which is excellent (and essential to understanding this dream world)

In fact, a self guided tour of Gaudi's Barcelona would be a fascinating thing to do and give purpose to the enjoyment of Barcelona. such a tour could include:
Sagrada Familia (done)
Parc Guell (done)
Casa Batllo
Casa Mila`
Palau Guell
Crypt of the Church of Colonia Guell

And, for those looking for a day trip out of Barcelona try the Monastery of Monserrat and the Black Madonna.

Barcelona is such a cool city. We really enjoyed touring La Pedrera and would have liked some time to tour around the whole Olympic stadium site and the Spanish Village that is there in the Montjuic site

Since the original question referred (and I definitely agree with the recommendations within Barcelona) to touring around Barcelona, I would add Tarragona to the already mentioned walled city of Girona. I would specifically mention the old city, the port, the beaches and coves typical to the region, the Roman Amphitheatre, all just an hour's drive from Barcelona. Beautiful city.