Register and make yourself known at the Pond (forum) or subscribe to the discussions by email. Read the Chronicle for the latest news. Explore the Wiki and suggest some features you'd like to see. Go hunting for bugs in the Trunk (the latest source code right in the subversion repository). You can see how development is progressing, checkout the source code and get a glimpse of the roadmap of the green future - just dive right in.
If you're not a developer, then it will really help if you can explain to the developer tadpoles what they should be doing. This CMS needs your ideas!