Announcing my new G2 Image Block plugin/widget. I don't use WPG2, and I recently converted my theme to be widgitized. Yeah, I know, what took me so long, but until 2.5 it just didn't seem to work right.
Anyhow, if you use Gallery2 outside of WordPress like I do, and you want to use the ImageBlock module for G2 in your WordPress sidebar, this plugin is for you. All of the listed G2 Image Block options are included, but I don't claim to have tested all of them. The sample I tried worked as expected. Your mileage may vary.
Check out the plugin page.