There are many collaboration tools coming with web 2.0 that project managers will find usage for. Some will enrich communications, increase reach ability in the extended project team, develop and hold part of the project or product documentation, set up project related professional networks, facilitate brainstorming, and improve productivity.
Some can be obtained for free, others for money. Your requirements for confidentiality and security will play a key role in your selection process.
In the productivity improvement section, I'd like to mention tools that will help you get organized with tasks lists such as:
1. MS Outlook or Lotus Notes (yes, yes, I know that they are quite old but they are good collaboration tools)
2. and at least a dozen more web 2.0 tasks lists management tools
Also in this productivity section, I suggest that you review a tool to share presentations called slideshare. You will be able to share your presentations and get inspired by the works of others.
To facilitate Brainstorming sessions you may want to consider mind mapping tools:
1. A list with pointers on Wikipedia
2. Also, check out "100 Online Brainstorming Tools to Help You Think Outside the Box"
To set up project related social/professional networks:
1. Ning : an online free platform for people to create their own social networks:
2. WackWall is another free social network builder tool. Custom design, photo/video sharing, forums, blogs, events... and for free
3. Elgg to create your own social network, quickly and easily.
4. SocialGO for a full featured social networking website including autorizations and controls.
To produce collectively and manage project or product documentations including tasks lists plannings, user guides... we have the Wikis.
Many, many tools in this area and a matrix that I found to be quite handy to compare the features of some of the best ones.
To be reachable and join the extended team members: In addition to traditional email and SMS, consider Instant Messaging platforms (Messenger, Google talk, Skype...) that can be a bit disruptive but will certainly help reduce significantly your volume of emails, also newer ones, especially mobile ready ones that can add value like Twitter with it's very short messages approach that force people to be concise.
And do not miss the much simpler web conference tools available since a few years.
What other Web 2.0 tools would you recommend?