Categorizing open source users
First I'd like to explain that I like to roughly categorize people involved in open source like thus:
Contributors - these are the guys and gals at the pit-face, developing software, writing documentation and generally striving to make an open source product better.
Investors - these individuals use open source software and help to make the product better via feedback and raising, and following up, issues (probably as it is in their interest to do so).
Benefactors - usually companies that give tools to open source developers or sponsor a project in other ways i.e. free licenses or free hosting e.g. NDepend, JetBrains and GitHub.
Angels - these people provide invaluable advice in just managing a open source project and may not be actively involved in the development itself but just keep you sane.
Community - Our main user base, users of open source but don't actively contribute back and hence why sometimes I refer to them as Welfare. Maybe in the case of the this group it is just a failure to engage, the product just works and they have no need to be involved outside of viewing forums and stackoverflow. But I feel that without the involvement of this group a lot of open source software, no matter how good, can fall by the wayside.
But how do we get them involved? Well first we have to find them, in my case with PartCover as the project had been abandoned the users stopped raising issues on the SourceForge forums and tended to ask questions on other outlets such as StackOverflow, SharpDevelop or Gallio forums and mailing lists.
Finding the users
I scoured the internet and compiled a list of popular places that PartCover was mentioned or supported. I was surprised to find that PartCover was used or supported by SharpDevelop, TeamCity and TypeMock amongst others (and yet again I am surprised it was abandoned and not adopted by anyone sooner).
StackOverflow seems to be the main place where people ask questions and to keep track of questions I have subscribed to an RSS feed for the partcover tag; and as soon as an opencover tag becomes available, or I get enough rep to create it, I'll subscribe to that.
Twitter is also quite a common medium nowadays so I have also set up the following search filter "opencover OR partcover -rt -via" to see if anyone mentions either of the projects.
Engaging the users
Now I have found the users, or the majority of, I started notifying these lists, forums and projects that PartCover was alive again (and I have started to do the same to inform them about OpenCover). Hopefully bringing them back or at least notifying them that if they have really big issues there is somewhere to go.
Involving the Community users
This is the big ask and I don't have an answer. If the product works then they don't need to talk to the forums or declare their appreciation of a job well done. I think sites like ohloh are trying to address the balance. Some OS projects have a donate button, but I am not sure we are doing open source for money, though some projects do eventually go commercial, anyone else can pick up the original code and develop it. Maybe the users don't know how to be involved, in the case of my OS projects they are quite specialised and the learning curve may be too much for some. But I don't think you have to just be involved in projects you use a lot.
Possible ways to get involved
If you are good at graphics why not offer to knock up some graphics for use on web-sites and in the application. [I am quite lucky that Danial Palme added support for PartCover and OpenCover to his Report Generator tool and has done a much better job than I would ever do.]
If you are good at installers, or even if you want to learn more about them, offer to manage them on behalf of the project.
If there is a project you like, support them on the forums like StackOverflow and help other users.
Perhaps update the wikis and forums, sometimes the users know how a product works or can be used better then the developers.
If your company uses a lot of open source, why not buy some licenses for useful software tools and donate them, geeks love shiny new toys; quite a few vendors such as NDepend will donate licenses to open source projects.
If you have an issue, try to help the developers as much as possible to resolve it by supplying as much information as you can and repeatable samples, remember the developers are international and doing this in their own time (as you probably know trying to repeat a scenario from scant information is very frustrating) and maintain contact whilst it is being resolved and let them know when it is.
Okay that's me done on the subject for now, suggestions anyone?