Extreme Planning by Mike Griffiths spells out the common sense idea that project planning for software development is not just a big plan up front that never changes, but more of an iterative process that evolves as the solution is developed. Software development projects are difficult to accurately schedule up front, because there are too many unknowns, and every software development project is different. But, over time, you can iterate to a more detailed plan as more is known. This article gives some good advice for planning a software development project. (Registration with Gantthead.com is required, but free!)