The great Joomla component Phoca Gallery allow easy picture management in your Joomla website. However picture description doesn't show up during slideshows. Here is a little patch to add this missing feature (for Phoca Gallery v2.5.0): phoca_gallery_with_description_in_slideshow.diff
To apply this patch, move to your Joomla website root folder and execute:
patch -p0 < phoca_gallery_with_description_in_slideshow.diff
You may want to make sure picture description is enabled in the component preferences. In section "Detail View Settings", "Detail Window" has to be a "modal popup box". Then in the section "Description Settings", change the option "Display Description" to "Show (normal)" or "Show (lightbox)".