Joel Spolsky takes a little time getting to the point, but it's a good one:
A top-quality software product is achieved incrementally:
Commercial software—the kind you sell to other people—is a game of inches.
Every day you make a tiny bit of progress. You make one thing just a smidgen better. You make the alarm clock default to 7:00am instead of 12:00 midnight. A tiny improvement that will barely benefit anyone. One inch.
There are thousands and tens of thousands of these tiny things.
This past week I began contributing to the development team's wiki: a compendium of product management information that includes everything from profiles of our competitors, to product plans for the next year or so, to resources for software engineers like tips on debugging. Just a few pages, but they will make the wiki just a bit more useful, and therefore make it just a bit more likely that other people on the team will contribute and read. And ultimately, our product line will be just a bit better.