POD (sometimes also referred to as POTD) is an acronym for Picture Of (The) Day.
Some web sites publish a new image every day and Pic-a-POD is designed to gather these PODs for you easily and quickly every day.
If you know of any other sites that have a POD, please let me know. The site must have a regular format with new pictures at least every week day, and they must have a large version of the picture available for download.