OpenLog is an open source project to create a simple to use data logger. 

OpenLog v1 is stable but only supports FAT16 and up to 2GB.
OpenLog v2 is a bit buggy but supports FAT32 and SD cards up to 16GB.

The hardware design and firmware are released under CC-SA v3 license.
The FAT16/FAT32 firmware was originally designed by Roland Riegel and is released under GPL v2.
OpenLog v2.0 and above uses sdfatlib written by Bill Greiman and is released under GPL v3.
The OpenLog firmware was created by SparkFun Electronics.

v1.0 Buggy initial release
v1.1 Small changes to system settings and EEPROM storage.
v1.2 Added wild card to listing and remove commands. Added read file command.
v1.3 Added auto buffer record if unit sits idle for more than 5 seconds.
v1.4 Increase buffer size to 900 bytes. Pinning down URU errors.
v1.5 Lowered power consumption to ~2mA avg. Added 4800 and 19200 baud rates.
v1.51 Added configurable escape character, and escape character amount.
v1.6 Added ability to configure via config.txt file.
v2.0 Massive overhaul. Ported to sdfatlib. Now supports FAT16/FAT32/SD/SDHC.
v2.1 Power save not working. Fixed issue 35. Dropping characters at 57600bps.
v2.11 Tested with 16GB microSD. Fixed issues 30 & 34. Re-enable power save.
v2.2 Modified append_file() to use a single buffer. Increased HardwareSerial.cpp buffer to 512 bytes.
v2.21 ringp fork brought in. rm dir, cd .., and wildcards now work!
v2.3 Migrated to v10.10.10 of sdfatlib. Moved to inline RX interrupt and buffer.
v2.4 Merged ringp updates. Commands cd, rm, ls work again!
v2.41 Power loss bug fixed. Adding support for 38400bps for testing with SparkFum 9DOF IMU logging. 
v2.5 Added software reset command. Modified the read command to print extended ASCII characters.
v2.51 Changed command prompt control to ignore \n for easier control from microcontroller.