What plugin does this? Please, help me!

On my side bar, I have a widget on top that shows the posts I want under a certain cat. In this case it’s videos of the month. What can I use to put an archive of only the videos of the month without having all the other categories show? Am I crazy? Is this a plugin that already exists? Can someone tell me how I can accomplish that?

http://www.yourpetsuniverse.com

I’d really appreciate all your input!