If Parliament is sitting, you may need to queue up to visit the Public Gallery of both houses.
If Parliament isn't sitting, you can walk in and out of the Public Galleries as you please (including weekends).
You wont be able to sit in the chamber itself (where the members sit).
This is the view you could expect
http://www.evandavis.id.au/canberra/houseofreps.jpg
Basically you are allowed free access to the Public Galleries of both houses, The Great Hall, the Cafe (it's crap!) and the various galleries (mainly pieces of art and pictures of current and former members).
You wont be able to go into other working areas.
Evan :->