Hello, Navid.
Unfortunately, we do not have an I2C library for the Baby Orangutan controllers. However, this post, “I2C Master routines for Baby O”, might be useful to you. In addition, more details on the I2C/TWI interface of the ATmega328p, which is the chip used on the Baby Orangutan, are available in its datasheet.
You might also try searching on AVR specific forums such as AVR Freaks for examples.
-Amanda