Watch this YouTube video showing how an HTML photo gallery created inside Picasa looks like - took less than a minute to create the entire photo album.
To create a Photo album in Picasa, select the photos and put them in the Picasa tray by clicking the Hold button. Next goto Album - Export as HTML page. Select the picture size, web album template and click export. That's it.
While Picasa comes with an impressive array of templates, you can download additional templates from paulvanroekel.nl The above picture gallery was created using the awesome LightBox Picasa template available here.
These templates are available as zip files - extract the content to the directory \Program Files\Picasa 2\web\templates\ in separate folders.