Swiss System is a tournament format that uses a set number of rounds, usually 5 or more. There is no elimination, so everybody in the tournament plays the number of rounds the tournament has. After each round, players are paired against other participants that have roughly the same number of wins and losses. The system is predominately used in Chess tournaments, and I'm pretty sure more information can be found at
www.uschess.org
While a Double Elimination system is very accurate at telling you who the top three are in a given tournament, a Swiss System is much more accurate when getting lower into the list of players. Here is a quick example...
4 rounds
12 participants
round 1
1vs7 winner=1
2vs8 winner=2
3vs9 winner=9
4vs10 winner=4
5vs11 winner=5
6vs12 winner=6
round 2
1vs5
2vs6
4vs9
3vs10
7vs11
8vs12
Now I only went over the first two rounds, but I think you can get the point. You can probably Google the term or ask Jeeves and get a much better answer. It's a pretty popular system for certain types of tournaments, again namely Chess. In chess however, the parings also take into account the color of each player in the previous round. So for example say, a Smash tournament using Swiss would pair players 1vs3 and 2vs4, if 1 and 3 were both black last round, and 2 and 4 were both white, a chess tournament would pair 1vs4 and 2vs3. Another thing to take note of is that in traditional swiss system tournaments, no two players will play each other more than once. In smash this would be a slightly bigger problem than in chess, because in chess there is the possibility of a draw, in which each players earn a half point (.5, where a win is 1 and a loss is 0). An advanced pairing system would be pretty usefull here.
Also, the East Coast tournament Getting Schooled 2 used a modified Swiss System format and featured over 100 players nation-wide. You can probably do a search here on smashboards to find out more about that.
Swiss System is pretty good, I think you guys'll like it ^_^