There is more to open source than a licence. It is also a development methodology. This page links to various resources about different aspects of open source development.
Documentation is key to the success of your project. If your users can't use the software then they will simply leave. If your potential developers do not know how to contribute they simply won't bother.
MarketingDocumentation consists of materials intended to attract potential users
UserDocumentation consists of materials aimed at guiding users through common tasks.
GovernanceDocumentation contains materials aimed at showing users and developers how to contribute to the project
DeveloperDocumentation consists of materials aimed at helping people improve the software and its documentation
[http://www.symphonious.net/2007/02/06/creating-great-documentation/ Creating great documentation]
[http://norman.walsh.name/2007/02/05/painting Topic oriented authoring]
[http://www.wikipatterns.com/display/wikipatterns/Wikipatterns Wiki patterns]
[http://www.onlamp.com/pub/a/onlamp/2007/06/14/why-do-people-write-free-documentation-results-of-a-survey.html Why Do People Write Free Documentation? Results of a Survey]
UsingSubversion - Subversion is a very common version control system that allows multiple people to work simultaneously on the same documents and code.
SoftwarePatch - Working with patches
["SVN Commit Messages"] - SVN can send out emails on every commit, great for peer review and keeping up to date
ContributorLicenceAgreements - a contributor licence agreement helps ensure that all contributions to the project can legally be included
Quality is key. This does not mean shipping without bugs, that is close to impossible, what it does mean is shipping with no known bugs (actually shipping early releases with known. but manageable bugs can be ok too). Testing is the way to ensure you are shipping (near) bug free code. Testing falls into two camps, user testing and automated testing. Both have their strengths and weaknesses.
[http://tapestryjava.blogspot.com/2007/05/free-and-excellent-code-coverage-for.html EMMA] code coverage plugin for Eclipse
Release Early, Release Often
Open source development is all about attracting users and developers. It is therefore important to release the software early, and as frequently as possible. Many people have difficulty with this concept, asking questions like "won't users be put off by the bugs?" Well, no, that is the point of open source, we are honest about our bugs and, if it really bothers you, you can fix it yourself (or pay someone to fix it).
Bugs exist in all software, not just open source. As long as you don't claim the software is more complete than it really is users will be happy to work around its limitations, safe in the knowledge that it is temporary.
More on ReleaseEarlyReleaseOften.
[wiki:ReleasingOpenSourceSoftware Releasing Open Source Software]
[http://en.wikipedia.org/wiki/Release_Management_method Wikipedia on Release Management Method]
[http://www.ics.uci.edu/~wscacchi/Papers/Open-Source-Research/OSSE3-Erenkrantz.pdf Release Management Within Open Source Projects by Justin R. Erenkrantz]
[http://www.tldp.org/HOWTO/Software-Release-Practice-HOWTO/ Software Release Practice HOWTO by Eric Steven Raymond]
You should make the installation of your software as easy as possible, ideally users should be able to download and install from a binary, whilst developers should have a clear document describing how to configure their environment.
IzPack - an installer generator for the Java platform.
OpenSourceDevelopmentInAction - a few examples of how doing it right saves time and effort later