Carcassonne is divided into two parts:
High speed TGV trains between Lille, Bruxelles, Dijon, Lyon, Marseille and Toulouse call at Carcassone. Slower Corail Téoz between Bordeaux, Marseille, Nice and Paris towards Cerbère and Port-Bou (and overnight Corail Lunéa couchette trains between Paris and Cerbère / Port-Bou) also stop.
An extensive network of frequent, modern and comfortable regional services are provided by SNCF's TER Languedoc-Roussillon , with services to Toulouse, Narbonne, Marseille, Cerbère, Perpignan, Limoux and Quillan.
Carcassonne Airport (IATA: CCF) is 3km from the centre of Carcassonne. Ryanair  serve the airport to/from Brussels( Charleroi) Cork, Dublin, Nottingham, Glasgow (Prestwick), Leeds/Bradford, Liverpool, London (Stansted), and Porto. A shuttle bus to the city centre via Chénier SNCF station (€5) meets every flight.
There is no left luggage at the train station.
You can leave your luggage at Hotel La Bastide Saint Louis (42 rue Barbes 11000 Carcassonne) for 1/2 day : €3 - Day : €5
Useful if you want visit Carcassonne city before your trip back from Carcassonne airport.
Historic fortress (built upon ruins predating Christianity). Carcassonne is an amazingly well preserved medieval fortress that was featured in the movie, Robin Hood - Prince of Thieves. Ville de Carcassonne is a beautiful castle and is the centerpiece of the medieval Carcassonne. It is a lovely place but can get very crowded at the height of the season.
Much to see in this somewhat neglected region of France. Get into the hills and visit little villages like Minerve. Try using the Michelin maps but forsake the red roads and take to the little white roads. You will be rewarded by seeing lovely little places that tour buses etc never visit.
Carcassonne can also be visited departing from Toulouse.
Medieval jousting displays are held twice a day between the two walls. Whilst this may sound like a typical tourist activity, this is actually a very impressive and entertaining display of horsemanship and combative competition. Entry is €10 for adults as of Summer 2008 - certainly one of best €10 that we we spent on our Summer trip.
If you're up to it, the Torture Museum is also worth a visit. It's small but filled with torture instruments from the Middle Ages. Not for the squeamish!
There are regular barge trips along the historic Canal du Midi, and these are a very relaxing way of spending some time. The boats leave from the jetty just outside the main train station, and tickets can be bought from clearly signposted vendors at the canal-side (just beside the lock). Multilingual commentary is provided on the history of the canal and the various sights along the way.
Festival de Carcassonne is held in July and August . Around half of July there is huge firework show (second biggest in France).
The eating places get crowded and the prices charged can be a bit over the top. Eat away from the cite, perhaps in the lower town, or better in one of the enchanting villages away from Carcassonne. Cassoulet will fill you full of beans and sausage in addition to the meat in there!
If you just wanna eat cheap, then the bars around the train station (la gare) should be good enough. There are also quite a few restaurants clustered around the main square in the Cite, the majority of which have outside tables so you can people-watch and enjoy the buzz of the square on summer evenings!
If your budget permits you, there are several excellent restaurants in the Cite, serving really good regional food. Among them are La Barbacane, Chez Saskia, Restaurant Comte Roger and the Brasserie le Donjon. These all serve divine food and the service is as you would expect - impeccable. As well as cassoulet, foie gras is a speciality of the region so expect it to be on most menus.
Be careful to not get to the town late when your hotel is far away from the city centre, because it is difficult to get a taxi.
The hotels around the train station are convenient but better book earlier in high season.