The Arduino platform lends itself nicely to data logging and working with a variety of sensors - and one example of this is by Willian Silver who shows how to measure temperature, humidity and dew point with an Arduino and LCD module. Furthermore the time and date is kept without using a RTC module, keeping the cost down (however it's recommended to use one for accuracy). The sensors used are easy to work with and once the system is completed it can also interface with WIllian's SCADA project mentioned that can be found in his code site.
For more information on this and other projects, visit Willian's code site. And for more, we're on twitter and Google+, so follow us for news and product updates as well.