Something that is done on another forum that I visit, I'll explain the whole system.
1. If a user has done something irritating multiple times that doesn't warrant a ban, that person is sent into "Purgatory". In Purgatory, the user is only able to view one forum. The only other people who can see that forum are other purgatory members, and staff members. The person can get out by proving to the staff that they have changed.
2. Another thing is a public bans forums. Anytime a person is banned/sent to purgatory, a topic is made here by the banner. The topic follows a pattern, outlining and providing links and reasoning behind the ban. Users can agree or disagree. If the majority opinion is towards disagree, the user may be unbanned or removed from purgatory.
The purgatory I could see being implemented here, but the public bans forum I doubt would be a success. The community is probably too large here for that.