Looking for plugins/ widgets

Hi all,

I’m looking for a plugin/ widget that does the following:

User can, from the dashboard, upload images.
plugin will generate thumbnails of a group of images, visible on website
as a site visitor mouses over a thumbnail, a larger version pops up.

Anyone know of anything like this, if not, can you point me to some beginner info on writing my own plugin?

Any help is greatly appreciated!