Long time ago, before even starting blogs, I've already had a fully working market screen. Since then a lot happened - new icon system, general purpose UI components, some UI concept changes, migration from xml's to sqlite database, so I had to rebuild it. This new version is cooler both inside and outside, the code is more organized and the UI has more decent look and some new useful features.
The main idea of the market is that various traders and their offers are unlocked through the game and fills the market to certain (upgradable) limit. The offers are limited by time and as they expired or fulfilled the market will replace them with new ones. There's a lot of offers, for both buying and selling various goods, you can buy the resources you need or sell excesses, or even find some blueprints and items obtainable only from the market offer.