here. It may also be possible for your MP to arrange a tour (group or individual). Contact details of MPs are available here.
If a visit to London isn't possible (and because of the sitting times - most tours need to start at a time when rail companies charge their peak fares) you can do a virtual tour.
There are a number of guides to Parliament available - the ones I use most often (for revision purposes before I take a tour round) are - The Houses of Parliament: A Guide to the Palace of Westminster (Fell; Mackenzie & Natzler - 15th Edition, 2002 TSO - currently out of print); Westminster Hall: Nine Hundred Years of History (Gerhold - James & James); The Story of Parliament in the Palace of Westminster (Field - James & James) and Dod's History of Parliament.