Here's a brief history for those interested...
The NSL started in Oz back in 1977 and has changed formats heaps of times since then. It started off as a first-past-the-post league and actually enjoyed large crowds and lots of sponsorship (It was Australia's first truely National sporting competition). In the mid 80's, the league was then split into 2 - the Northern Division, comprising of teams from NSW and ACT, and the Southern Division, with teams from Victoria, Sth Aust, and Queensland (strange but true). A top 5 Finals series was introduced for each Division, with the winners from each Division playing off against each other for the National League Championship. This format lasted until the late 80's and was changed back to a single first-past-the-post division league in '87. In '88 the finals series was re-introduced to try and earn extra money for the NSL, and to add more excitement back into the league. The early 90's saw the NSL disposal of the traditional promotion/ relegation system, instead opting to focus on just the same clubs year in, year out. It was also changed from a winter league to a summer league. Several clubs have come and gone in that time, namely Collingwood, Carlton, Morwell/Eastern Pride & Canberra Cosmos. Others have taken their place with various degrees of success.. Perth Glory, Parramatta, Northern Spirit.
South Melbourne, Marconi, and Adelaide City are the only clubs that have played in every season since 1977. Olympic Sharks have missed just one season (1979 i think). Sydney Utd, Melbourne Knights have been in since 1984, and Wollongong Wolves(86) are the next longest servants. Brisbane Strikers and Newcastle Breakers joined in the early 90's, followed by Perth, Northern Spirit and Parramatta later on in the decade. The NSL is also the only league in the world that has a team from another country playing in it, the Football Kingz from New Zealand. They also joined late in the 90's.
Here is a list of the NSL Champions to date:
Sydney City * 1977
Adelaide Sharks * 1978
Marconi Stallions 1979
Heidelberg * 1980
Sydney City * 1981
Sydney City * 1982
St George * 1983
South Melbourne SC 1984
Brunswick Juventus* 1985
Adelaide City Force 1986
Apia Leichhardt * 1987
Marconi Stallions 1988
Marconi Stallions 1989
Olympic Sharks 1989-90
South Melbourne SC 1990-91
Adelaide City Force 1991-92
Marconi Stallions 1992-93
Adelaide City Force 1993-94
Melbourne Knights 1994-95
Melbourne Knights 1995-96
Brisbane Strikers 1996-97
South Melbourne SC 1997-98
South Melbourne SC 1998-99
Wollongong Wolves 1999-00
Wollongong Wolves 2000-01
Olympic Sharks 2001-02
Note: Clubs with * are no longer in the NSL.
I hope i havent left anything out
