Scioly.org

Nope, but most likely you aren't going to find one. Most sites that have games on them aren't going to go into the topic enough for science olympiad.
But this site has a lot of excelent info. If you haven't started your research yet, start at the Meteorology Wiki.

Interactive games aren't the best, remember you do get a page of notes front and back that can help- as long as you know where everything is. There's a lot of information everywhere on the internet. It's all about knowing where to look. The wiki's a good place to start.

Does anyone know any good website for studying metar?

You should start at the [wiki][/wiki], more specificly the Meteorology Wiki, or try Googling it

okay, cool

Or you could look at robotman's sig...

what is the difference between relative humidity and dew point?

the dew point is what the temperature would have to reach in order to lose its ability to maintain any moisture. For example, if the dew point was 50 degrees F, and the current temperature was 100 degrees F, then if for some reason the temperature suddenly dropped 50 degrees the air would lose its ability to maintain moisture, and it would get very humid.
Relative humidity is what you get when you divide the dewpoint by the temperature and multiply by 100. So if the dewpoint is 50 degrees and the temperature is 50 degrees, you would have 100% relative humidity. If the dewpoint was 50 degrees and the temperature was 100 degrees, you would have 50% relative humidity.

OK that will help me

What was on your State Meteorology test?