Online casinos are running slot tournaments constantly. If you are from the U.S. and are interested in playing in an online slot tournament (and many are free to enter) join either SuperSlots or English Harbour. They both take players from the States and run tournaments non-stop.
Good question. In a slot tournament, players each pay to enter. Some tournaments don't charge a fee (they're called "freerolls"), most fees are super-reasonable. I see a lot of them in the $5-$10 range.
Once you pay your fee, you begin on a slot machine with a set amount of credits. You play, and try to build up your credits as high as you can. Hopefully you build them higher than the other players in the tournament.
Once the alloted amount of time is over, the players with the most credits win.
What Do you Win?
You win part of the prize pool. The casino takes everybody's entry fees and put them together, the winnings come out of there. So, if you paid $5 to play in a TombRaider slot tournament, and won with a total of $61,000 in credits, you're not winning $61,000. The credits you rack up on the machine are only tournament credits.
Some slot tournaments have guaranteed prize pools that the casino puts money towards (in addition to the player's entry fees), and they can have some really nice prizes.
What's a Rebuy?
If you enter a tournament, play, and find your credit count going all the way down to zero, you may be allowed to try it again. You just pay another fee, a "rebuy fee" to have another try.,p>
Sometimes the machine they're using for the tournament is a particularly fun one. Sometimes the leader has a score that's not particularly high, and you think you can get there in a couple of tries. rebuys are just a way to say "I want another chance at this" in a slot tournament.
Other Regular Slot Tournament Action
All Jackpots Casino - Steady Slot Tournament Action
They run a steady stream of tournaments at All Jackpots Casino. Slot tournaments are popular, and casinos definitely want to keep their slot players happy.