Spirit points are used by some leagues and tournaments as a way of measuring and rewarding teams that uphold the Spirit of the Game.
The systems used by different leagues will vary greatly, but in general, spirit points are allocated on some sort of numeric scale (1-5 and 1-10 being popular), with higher being better. The points are allocated to each team by their opponents, who rate them after each game. At the end of the competition, the team with the highest score, or highest average score, receives the league or tournament spirit prize.
Attempting to measure an intangible on a numeric scale undoubtedly meets with problems, the most obvious of which is that since few people agree on what exactly "spirit" is, two people rating the same team for the same game will likely come up with different scores. However, this is the same problem faced by many judged sports (diving, figure skating, gymnastics) and the problems can be solved in a similar manner if the league organizers or tournament directors are so inclined.
At UK tournaments, each team will vote for 1 or 3 teams they think were most spirited over the whole tournament. Votes are collected after the final; the winner having most votes.