Basecamp is great tool for lightweight project management. It won't solve your motivation problem but it will make it easy to keep things organized. My suggest

Basecamp is great tool for lightweight project management. It won't solve your motivation problem but it will make it easy to keep things organized. My suggestion: make a to do list about a particular function/feature and quickly jot down those tasks needed to make things happen. Any time the planning urge strikes you jot down some more. After a while you'll have a decent backlog of work to chew through. When you're feeling less motivated about work and planning start working your way through that list. This prevents you from trying to force yourself to plan when you run out of things to do. The key to project management is the same programming. Keep breaking up the problem into smaller chunks that are easily tackled. Find the quickest system that allows you to document this without spending more time figuring out a new PM tool on top of your normal priorities.