Dependency Injection Hooks - we could take a page from asp.net mvc book and provide hooks for DI. A good place for that
would be registering attributes or provide hooks to register field indexers by type info or names.
Hackathon during ApacheCon ?
Maybe hold biannual Hackathons in the spring and fall of each year.
Maybe do something like RailsRumble and has a site that lets teams of people work on small projects.
Add Lucene.net driven search to the incubation/lucene.net site
StackOverflow Question Feed.
Create a crawler for looking for sites and articles that have to do with lucene.net