First look for content that every member of the community needs access to and which is updated on a regular basis. This could be project specific content, such as weekly progress reports and project time-lines, or it could be more general information such as an employee list or HR policy and procedure documents.
Also consider loading any style guides and project management documents that you regularly use.
Consider including email traffic within the community or even transcribe water cooler and hallway conversations (after you’ve asked the other person’s permission of course!). Are there particular projects and subjects that are often discussed and debated within the team? What things spark the biggest and most sustained email threads? Consider adding background documentation with discussion pages.
And if the wiki is being set up to manage a particular project, make sure to load all the relevant project information and documents.
Whatever you choose, make sure it is information that people use. Seeding a wiki with dead information means it will remain dormant.