NET.exe

The NET Command is used to manage open files and user sessions as follows:

Display all the open shared files on a server and the lock-id
NET FILE

Close a shared file (disconnect other users and remove file locks)
NET FILE id /CLOSE

List all sessions connected to this machine:
NET SESSION
or
NET SESSION | Find "\\"

List sessions from a given machine
NET SESSION \\ComputerName

Disconnect all sessions connected to this machine
NET SESSION /DELETE

Disconnect all sessions connected to this machine (without any prompts)
NET SESSION /DELETE /y

Disconnect sessions from a given machine
NET SESSION \\ComputerName /DELETE

Notes:
NET SESSION displays incoming connections only, in other words it must be run on the machine that is acting as the server.

To create file shares the SERVER service must be running, which in turn requires 'File and Print Sharing' to be installed.

“Never mistake activity for achievement” - John Wooden

Related:

NET - Manage network resources
NET USE - connect to a file share
GLOBAL - Display membership of global groups
LOCAL - Display membership of local groups
OPENFILES - List or disconnect open files, local or remote (Win XP)
PsFile - Show files opened remotely
PsLoggedOn - Who's logged on
fsmgmt.msc - List or disconnect open files - (Win XP GUI)
Drmapsrv - Drive Share for use with Terminal Services (Win 2K Server Resource Kit only)
Q149427 - Change Password from the CMD prompt
Slow Network Browsing (XP)
Powershell: Get-WmiObject win32_share
Equivalent bash command (Linux): who currently logged in