Add a PicLens Slideshow to Gallery. ***NOTE: PicLens is now called Cooliris, but the plugin in G2 was created before that change happened so there are references to PicLens.
The "[core] item view" permission determines whether a user or a group has permission to see a slideshow in a specific album. If the user has permission to see the slideshow, G2 automatically adds a "view slideshow" link in the item action links block.
You can get an updated version that allows control over the size of the images displayed as well as the delay between images here:
FlashYourWeb Slideshow update for G2 - thanks suprsidr!
Forum thread about it here: http://galleryproject.org/node/82813
To install that update, you'll need to uninstall and delete the Slideshow plugin that comes with G2. Then you can download the update from suprsidr's site above, unzip it, and upload the slideshow directory into your modules directory so it should be located at modules/slideshow Then go to Site Admin > Plugins and activate the Slideshow plugin.
Once that's done you can go to Site Admin > Slideshow and install or uninstall the Cooliris plugin
***NOTE: This update also changes reference from PicLens to Cooliris.