The process explorer is a great tool from Microsoft (they bought SysInternals).
Nice things
Find a process that look a specific file
Click: Find->Find Handle or dll..
In the textbox "Handle or DLL substring" type in what causes the look
Example: ErrorLog.txt
And all the processes that hold a lock on that file are showed.
List number of objects in the finalize queue
Press the .NET tab.
Select ".NET CLR Memory" from the drop down
In the field "Finalization survivors" it stands how many objects that survive the last garbage collection.
Tips: for a more advanced view of the finalize queue use
WinDbg
External links
Process Explorer
Run Process Explorer (from SysInternals)