[mrsmith]

http://www.onlineconversion.com/
Just great for navigating through all the crazy units the world uses.

http://www.mathopenref.com/graphfunctions.html
No calculus? No problem!
Site lets you compare three equations with whatever variables. Wonderful for musing out equations.

http://www.cpc.ncep.noaa.gov/products/OUTLOOKS_index.shtml
Right at least half the time!

[be-baw]

Siri on my iPhone gives quick conversions. For example, I just asked how many dashes in 1 fluid ounce. Answer: 48.

[mrsmith]

Come on. Share those sites.
They may be specialized- so? Some Freeper may need that speciality one day.