Wikimedia
Wikipedia: Absolute Zero
Wikipedia offers several paragraphs of detailed information on absolute zero, the lowest temperature that can be obtained in any macroscopic system.
Other
Science Made Simple: Temperature Conversions
Science Made Simple allows you to type in temperatures you want converted from one measurement scale to another.
US Navy
Naval Research Office: Ocean Water: Temperature Scales
For an overview of the four temperature scales, visit this site. General information is given about the scales including their boiling and melting points.
Science4Fun
Science4 Fun: Temperature
Discover interesting facts about temperature and learn the different ways it is measured.