If you have a technologically talented team member, you can create a shared workspace in-house for free (not counting labor costs) using open source wikis. A wiki is software that creates Web sites that can be written and edited by a community. Your team can post ideas and updates and have discussions online using wikis.
Unlike Microsoft SharePoint, a wiki-based intranet allows anyone to edit content. If you choose this solution, make sure you create and enforce a policy for acceptable use. You might also want to back up the site often to stop accidental changes from losing information permanently.