I just ran across this post by Greg Notess:  SearchTeam: Collaborative Asynchronous Searching — looks like it has lots of possibilities, especially if you are working on a group research project — or any other type of collective activity.

Positives

1. It accepts logins from other sites (don’t have to create a new account/login)
2. Doesn’t require simultaneous online presence
3. Has a Team Chat function
4. Searches beyond webpages – databases of videos, images, books and more
5. Free although at some point premium features may have a cost attached
6. Provides suggested search terminology

Another tool in the buffet of resources!