I hardly ever write reviews but this one really is a gem... I have spent hours searching for a gallery mod that would integrate with Picasa and display only the albums I wanted with pop out lightbox, it also integrates with facebook albums but I have not used this feature so cannot comment. However, when using picasa albums This does it perfectly (and more). The mod is highly customisable, the accompanying documentation good and the forum well monitored and supported.
I would highly recommend this to anyone wanting to put a gallery on their site, it can take a little perseverance when getting to change some of the more intricate elements but it is well worth is as you will have a very customisable gallery. Also.. check out accompanying mods such as the Phoca Gallery Image Mod which are very easy to use and create some wonderful elements to any site.