This simple one liner is a drag and drop script.
It assumes that you have 7zip and it is located in your path, if not add the the directory to your path variables, or put 7z.exe and 7z.dll in the desired directory with this script.
Simply drag your file or directory over the batch to compress files.

Code:
@echo off

::
REM This is a drag and drop script that uses 7zip to compress files
REM Simply drag the file or directory over this script to compress it
::

7z a %1.7z %1

PAUSE