Practically speaking any development board can serve as simple datalogger. The only question where this data is gonna be stored. During long time periods there can be tons of data collected. As internal memory of microcontroller is very limited, there are two options. On is to store data to external media like SD card or send data to PC via one of available interfaces like RS232, USB or Ethernet.
chris decided to build a logger board that is equipped with necessary interfaces (RS232, Ethernet, SD/MMC) and even prototype area for custom circuit. Board is designed to be low power and is operating from 3.3V.