Commercial applications are distributed on The AppExchange. You can also move code from one org to another using unmanaged packages, the metadata API and change set functionality.

Overview

• Publish Your First App with AppExchange Checkout - A detailed step by step guide on publishing your first app on the AppExchange.
• ISVForce Guide - A Must Read! This guide is written for independent software vendors (ISVs) who want to sell applications built on the Force.com platform. It covers the entire lifecycle of a packaged application.
• An Introduction to Packaging - This article provides an introduction to packaging and distribution on the Force.com platform

Resources

• How to Create a Trial on AppExchange - Learn how to create trial environments pre-populated with an application and sample data.
• Introduction to Developing Commercial Apps on Force.com - The process of building and distributing commercial applications for ISVs.
• Releasing an Application on Force.com - How to prepare your application for commercial release.
• An Introduction to Environments - An outline of the various environment editions which your customers may be using.
• An Introduction to Force.com Metadata - Note how the Metadata API and Force.com Migration Tool can be used.
• How to Create and Register a Package - Walks you through the process of creating, uploading and registering a package.
• Push Patch Updates - Quick overview of the Push Patch Update feature introduced with Summer '10. This technology enables ISVs to seamlessly push out managed package patches to their customers.
• Designing an Application for Group and Professional Edition - This article is intended for partners planning to sell an application to GE and PE customers.
• Creating an AppExchange Listing - With the new AppExchange, you can start creating your listing while your developer builds the app. You can then associate the listing with the app when ready, or follow the steps here to upload a package and list it. The new listing wizard in the AppExchange offers contextual help to guide you through the listing process.
• Publisher's Toolkit - The latest resources that will help you market your app on the AppExchange are available in the Partner Portal
• LMA 2.0 Overview - Overview of License Management App 2.0, includes a great demo of associating the License Management Org (LMO) and managing customer licenses (Recorded Webinar)

Videos

• Watch the AppExchange for Developers: Monetize Your App in the Cloud webinar.
• Watch the Team Development and Release Management for ISVs recording from Dreamforce '12.

Discussion Board

• AppExchange and Packaging Board

Official Documentation

PDF

How IT can plan, build, test, and deploy Force.com applications using a combination of Web-based and traditional development practices.

PDF

Everything you need to know if you're a developer building an app that will eventually be packaged on AppExchange.

PDF

How to publish an app or service on AppExchange so that it's available to external customers.

PDF

How to download apps into a Salesforce.com organization.