I just created and published my first library! 
It creates a Trivial File Transfer Protocol (TFTP) server on a particle device in order to download or upload files stored on an SD card over Wi-Fi. TFTP is easy to use since it only supports PUT and GET methods and that also means it should be a little more lightweight than regular FTP. On the downside, it has no directory listing capability so you will need to know the name of the file you want to download.
See the repo for documentation and an example: https://github.com/abelsm2/TftpServer
I’ve tested it on a Photon. I have a P1 that I will test very soon as well.