Download link: olpc-os885-rpi.zip
543 MB download, meant to be written to a 2 GB SD card with a tool like dd (under Linux) or Win32diskimager (under Windows)

Based on the official OLPC image for the XO-1.75 from http://one.laptop.org/ + Raspberry Pi kernel.
Currently disabled/broken activities: Wikipedia (use the normal web browser instead)