- the Case Batch Export Family RFA's tool
This way is pretty robust, as it also gives you a list of inplace families and masses that it couldn't save to rfas. Unfortunately, it is pretty hard to get now that Case have shut down their free app downloads :( Hopefully someone in your office already has it installed? Just copy all the files starting with Case between the relevant addin folders to get it going.
- You could also use the builtin method File - Save As - Library - Family - All Families to export the rfas, and then (for 2013 version only) the free Kiwi Codes Family Categorizer to sort them into Category folders. More on that here:
Personally, I now usually use Unifi to export and manage Revit content.
Thanks to Matt Wash for prompting me to do an update post on these different methods.