Seating arrangements. Be it putting people who work well together in adjacent offices, or on adjacent tables.
Giving people freedom and allowance for failure, not having a strict "I am the boss" micromanaging hierarchy on the team.
Reward people for taking initiative. Find work that people want to do, and give them time to do it on their own but only if they self organize all of it, this builds necessary skills.
Taking someone who looks like they may have leadership potential aside and asking them to take on a small feature.
Combine all these together and you'll come in one day and find your team in a huddle tackling tasks together.
Requirements: Not being an insecure manager. Knowing that your value to the team and org is not in telling people what to do, but rather in helping them do what needs to be done. Sometimes this means communicating directives from on high, other times it means getting the team the resources that they've determined they need.
Interesting. I wish there was a bit more detail on how you organize them to do so...