Who's logged into the domain?

From the server, right-click "My Computer" then click "Manage".

Expand "Shared Folders" then you can either click on "Sessions" or "Open Files" to see which files users have open.

waynewilliams comment will work, but it will only show you users that are currently utilizing a file on the servers file share.

I see what you mean CreditSoupTech.  As the author is using SBS 2003 I was assuming that it would be a single server environment with all shares on the same box.  Not always the case I know.

I was looking into the program "psloggedon" (program mentioned by creditsouptech. The program is good, but I don't think it will do enough for what I want. It kind just sees who is using resources remotly, which I guess would tell you who is logged on ,but I am looking for something else, perhaps more commercial.
Is there a tool/program that will tell you who is logged in, maybe a time of log in? Or if they are currently logged in now or logged off. I am not looking for anything like track4win which monitors what they do, simply just who is connected to the domain currently.

thanks for the help

You could look at the DC event viewer security audits logs, but that would suck. Maybe there is a program that simplifies or formats the event viewer in a report like fashion. I would start there. This would only tell you log on and log off.

There is a tool call Limit Login and its main purpose is to limit the number of concurrent user logins to a domain, but it can also be used to keep track of all logins in a domain. LimitLogon is an unsupported tool and can be downloaded here from Microsoft.