Atom - MSN Encarta (http://encarta.msn.com/encyclopedia_761567432_9/Atom.html):
    Ok, so it's not the most exciting article you've ever read, but it sure does give you a lot of information about the history of the Atomic Theory beginning with those of the Greeks.

Maxwellian Velocity Distribution (http://jersey.uoregon.edu/vlab/Balloon/):
    I saw this demonstrated in class and decided to search it out for myself. It demonstrates in a semi-hands-on way the effect of heat on pressure using the gas laws.

Chem4Kids.com: Matter: Changing States (http://www.chem4kids.com/files/matter_changes.html):
    If there's any confusion on this whole "phase change" thing, check out this website. Chem4Kids explains it in a way that even the college student can understand!

Gas Laws (http://library.thinkquest.org/12354/):
    If you want to learn anything about the gas laws, here it is. This site declares that it's "dedicated to teaching the ideal gas behavior" and it's not lying. Check it out!