Time Boxing

There is an interesting summary of the options when limiting the time and cost, or timeboxing, a piece of work. I think the dangers of increasing the cost to increase functionality, adding more people to a team to get more capacity are poorly covered. Fred Brooks said in the Mythical Man Month that "Adding manpower to a late software project makes it later." Adding people to a team to increase capacity late in a project is particularly dangerous in Software projects but perhaps less so in other activities.

http://tynerblain.com/blog/2006/04/12/how-to-use-timeboxes-for-scheduling-software-delivery/