This handy little SD card adapter is not just a breakout board but rather a feature rich adapter with a focus on ease of use.
It has an onboard regulator to provide 3.3V cards with more than enough power and also includes a 3.3V-to-5V level shifter. This means that you can easily add an SD card to 5V or 3V systems without the need of extra components, cool!
To use with an Arduino, connect GND to ground, 5V to 5V, CLK to pin 13, DO to pin 12, DI to pin 11, and CS to pin 10. Then you can use the wonderful SDfatLib which supports FAT and FAT32 SD cards. For details on getting started, check out the detailed tutorial discusses microSD cards, wiring and how to use this breakout board with an Arduino.
Dimensions (without 0.1" header):