FreeXperia is a SONY specific distribution for Xperia andriod devices (2011 onwards) based on the CyanogenMod ROM. These provide the latest version of android for all major handsets under the SONY banner. These are not stable ROM's and they are to be installed and used at your own discretion. Have fun with the latest features from Google directly to your phone :)
P.S. - I DO NOT OWN, and AM NOT A PART OF THE FXP TEAM itself... I simply am a common fan of the project, android, and Xperia, and wanted to get the word out there.