I just added this link to a Heat Index Calculator (thanks Danny!) - it's now in the "Useful Links" section on the side. Coming from a fairly dry part of the world, I never really thought much about humidity and the effects of wet air before. It seemed strange when people would exclaim about "85 degrees, and *85%* humidity!" I had no concept of what that felt like - how was that substantially different than just 85 degrees?
Hmmm - well! Since moving to the tropics, I have definitely seen what all the fuss is about! Humidity makes a difference. Still, it's funny when people say it "feels like" 120 degrees. Really, it "feels like" 90 degrees and 87% humidity. But then you realize it's all about the warnings - be careful of heat stroke, stay out of the heat, etc. I definitely took advantage of the cool pool when the heat and humidity spiked :-).
The thing I would like to see is some way to relate to cooler temperatures with high humidity. For example, in rainy season, my area very often is 70 degrees, with the humidity at 75% - that doesn't feel hotter, it feels clammy - aka yucky!