I noticed an interesting post from Allison Beckwith about Project Planning Grids. She also provided links to Todd Warfel's Task Analysis Grid and Blink Interactive's Objects & Actions Analysis. All three posts centered around different grid styles & focuses, but they all discussed ways to map out the different objects/features of a project in an easy-to-understand grid, so that you can flesh out requirements, standardize vocabulary, and understand which items need to be developed when.

Allison & Todd's grids felt higher-level, and included color & position to denote schedule & priority. Blink Interactive's grid was more detailed & was perhaps a better way to ensure you didn't miss a requirement. I could perhaps see starting with Blink's grid to round out your featureset, and then a grid like Allison or Todd's for planning & priority.

At DevelopmentNow we do a lot of project work, so one of the first things we do is map out a project featureset into "chunks" and rough feature descriptions, then assemble them into a basic dependency & delivery list. One of the big aspects in project management is getting scope right, and since there's always a tradeoff between delivery time & overall features, it's important to make sure that you haven't forgotten a critical feature, and that everyone (including and especially the client) understands what will be delivered when. So I can see how the additional dimensions in a grid, along with colors, can help add additional contextual scope information without sacrificing simplicity.

FYI, Todd actually prints out his grids on huge (like 6 feet wide) paper, puts them up on a wall, and talks through them with clients, allowing the client to write on the paper, interact with it, etc.

Some sample screenshots of grids below: