If you're using Access in shared mode, you might be wondering who's currently using the database.
Well this information is actually stored in the *.ldb file (pre Access 2007) or *.laccdb file (Access 2007).
This file automatically opens when you open your Access database in shared mode (this is the default - you can open a database in Exclusive Mode, through the options of the File/Open window) - it manages users and record locking in shared mode.
And you can actually read this file, you only need a more advanced text editor. However, Microsoft offers a special tool, called Jet utilities, containing a LDB viewer which withdraws more exact information about your connected users; you can download it here : http://support.microsoft.com/kb/176670. It also seems to working under Access 2007.
For any problems with the lockfile, you might go through this article: http://support.microsoft.com/kb/299373/EN-US/
And if you want to list users and access through VBA code, this is possible to; for a nice module on this topic go here: http://support.microsoft.com/kb/285822/