We will be in Toulouse,France for business (in mid-June) but have 4 extra days to explore once we have finished. I was at first thinking we would do Carcassonne, Collioure and maybe a day trip into Spain but am wondering if Provence would be a better option. Is 4 days too long for the Collioure area? This is at the end of a 2 week trip...
Collioure is a wonderful area and will provide a very laid back experience. Andorra might also be of interest. On the other hand, having a car and visiting the cities and towns of Provence is also wonderful. You really can't go wrong with doing either one. Spain is wonderful. I am not big on Carcassonne; I have been there a few times and almost enjoy seeing it from the outside now rather than go inside, but once should be something for everyone. Albi is worth a visit if you take this path also. I would then go down to Port Vendres area.
After a two week trip, I would choose the more relaxing trip and both can be that. Don't choose to see too much or your stress goes up and your relaxation goes down. Enjoy every moment.
You might also consider heading north, to the Lot, Cele, and Dordogne valleys. It's lovely country, and there is lots to see and do.
Provence is also compelling, but I would be slightly daunted if I had to spend the last night in Toulouse to fly home. If your plans are still flexible, though, you might return from Marseilles or even (via direct TGV from Avignon) Charles deGaulle.