Looking at your description
1. You have a very small team. 5 people is not a challenge for knowledge sharing.
2. You seem to want knowledge harvesting – News Articles, Public Opinion (polling data?) Tech Information
3. You seem to want collaboration tools – Links, Articles, Statistics/Graphs.
Start with a Base: A Sharepoint wiki would be fine, as would any other wiki-like software. I’m partial to TikiWiki and DokuWiki for complete nerd reasons. I’ve also used Basecamp for project management, I found it quite easy to use.