The following South Australian State Electoral Office website
explains the history of voting, different types of voting systems
used in Australia and their pros and cons as well as the merits of
compulsory voting:
http://www.seo.sa.gov.au/apps/news/?sectionID=41
This is provided by a delightful Macromedia Flash animation
[Macromedia Flash will need to to installed on your
computer;,it is available free on the website listed
above] which also graphically describes the counting
methods used for first past the post, prefrential approaches like
bottoms up and proportional representation:
levelCMS