If you have your photos on Picasaweb as I do, and want to display them with some commentary, this is a no-brainer Gallery plugin for WordPress.
In fact, the Gallery display beats Picasaweb itself I think. And the support from Mike Toppa and others is superb.
If you're looking at starting a site for showing photos, or even if you're wanting to display the occasional photo this plugin is well worth the time spent in familiarizing yourself with it.
Feature suggestion :
An older version allowed (or defaulted) the copying of photos into the WP Media section. The advantage to this is that then you can use images from Picasa as WP 'Featured' images supported by your theme.