What is an unmanaged package and how is it useful? An unmanaged package allows you to take a set of functionality (objects, fields, tabs, workflows, classes, pages etc.) and turn it into an installable link into any Salesforce.com org! This is very useful when you have an app you want to install in separate orgs (meaning separate production orgs, for sandbox to production in the same org you should use change sets).
Unmanaged means it is not published on the Appexchange and does not go through security review etc. An example of how this would be used is lets say you're a consultant and you developed a recruiting app that you want to install for different clients. You would create the recruiting app in a developer org, create an unmanaged package, then use the link to install the recruiting app into your clients orgs as needed. Click on the below link for a step by step guide I put together to show you how to create the package.