My county government agency utilizes SharePoint and it works wonderfully. I chair a state committee (as part of my county job) and would like to set up a seperate platform for users in the state group. They would not need email access, just access to a SharePoint site. Is that possible?
SharePoint supports multiple web applications (i.e. agency.domain.com, state.domain.com, etc..) and it also supports multiple site collections within the same web application, each having their own security. You can also create a subsite and restrict security there as well, though that would share other items with the parent site collection. That behavior may or may not be desirable.
Which method you chose depends on the level of isolation you need for the data and how you wish to access the data.