If you're talking about polls, bug tracking, forums, wikis, etc., almost any hosting service, such as SourceForge will provide you with them.
GoogleCode is more complicated, but you can put together many Google services (like GooglePages, GoogleGroups, etc.) to create what you need. I did once for one of my "future" projects (that is, those with which I start, and I never had time to complete :)): http://msqhome.co.nr . I also integrated Nabble for forums, I think that Google groups can be an obstacle for people who do not have a Google Account.
There are other services, of course, Wikipedia seems to have a good list.
If you are talking about how to make sure that people know about your project and are ready to work out or provide feedback, this is a completely different story. It depends on your project, how good it is in solving any real problem, etc.