The Server Processes screen
For example, in the above screen, there are 3 processes, one of them (638) is connected to a database named Northwind. The Info column holds the current SQL statement.
You can kill a process by using the Kill Process button, or using the context menu on the list of processes.
The Server Processes screen automatically refreshes the list every n seconds, where n can be adjusted using the spin edit box on the top right of the screen - this refreshing can be paused by checking the Paused checkbox and can be forced by using the Refresh button on the top left of the screen.