Displaying category thumbnails as a gallery.

Hey all,

I’m trying to have a sidebar that displays the featured images of posts in a certain category in two columns on the left, but when the thumbnail is clicked, it shows the large image to the right of that column.

I’ve been trying to find a tutorial for this, but I can’t seem to find anything or I can’t describe it well enough.

Does anyone know of good plugins or tutorials that could help me with this?

Much appreciated!