I visited the Ferrari factory the other week, and included a visit of the Lambo factory and museum. Cool visit -- with the Gallardo production line, things are more scaled-up than my last visit (2002). Chatted briefly with Valentino.
Tours are available, but you need to schedule them in advance. They are usually pretty accomodating, from my experience.
Directions are reasonably easy... I prefer to take SS 9 (Via Emilia -- the local highway that connects Bologna and Modena), and take the uschita (exit) heading for Nonantola. Follow the winding country road into Sant'Agata Bolognese, and the factory is right there.
I have been at the works last week and I was told that they're thinking of having paid visits round the factory within some time from now.
At present it's pretty difficult to get a tour as the Gallardo spyder is now being prepared for production.
I was lucky enough to be present a the revealing of the car and it looks pretty neat.
If you're a sincere Lamborghini enthousiast you should definately go to see the Tonino Lamborghini museum in Dosso (details on www.lamborghiniregistry.com).
Great museum. Loads of very, very rare cars. Bit tricky to make photo's though.