Quillan is good for XC (FFC centre vtt Aude en Pyranees), 30 mins further on over the col d’axat is the Capacir (les Angles, Formiguere), great area with lifts as well as XC. 30 min further gets you to La Molina bike park in spain, good stuff there.
There is also some good riding to the north east of Narbonne (Nevian, 30 mins), Fontfroide and Clape near Narbonne (30 mins) , inland from Perpignan (Agly, Ile sur tet, Cabanes de corbiers, Balesta) (1.30 ish), some stuff above fitou (45mins). There is a centre FFC vtt in the montagne noire just east of carcassone as well but its a bit crap.
http://www.utagawavtt.com/ Search under aude and pyranees orientale and you will find loads of stuff.
If you are down during the summer hols, do not try to go to any of these places on a saturday though. The 45 mins fitou to Carcassone took me 3 hours when I forgot this.