First, make sure that you have WPG2, a neat plugin by ozgreg and capt_kirk that embeds Gallery2 into WordPress.
Just download the archive and unzip it into the plugins directory, enable the plugins from the plugins tab, and then set up the widgets from the Presentation / Sidebard plugins tab.
The WPG2 Random Image widget can have several instances, and each one can take a random image from a different album (or from the entire gallery if none is specified).
The WPG2 Grid Block is a widgetized wrapper for the standard WPG2 grid block, and it can take an optional album ID as well.
The properties for the sidebar images and the grid block can be modified from the WPG2 tab in the WP Administration interface.
WPG2 Widgets are released into the public domain for everyone to use and share. Have fun!
Q. I enabled the plugins and I don’t see a thing.
A. Make sure that WPG2 is running correctly. If you can’t see the WPG2 tab in the administration interface the Widgets won’t register themselves and you won’t see them.
What support? ;-)
Well, while basically you are on your own, if you run into trouble leave a comment and I’ll do my best to help you.