Photographic Calculators around???

Does ANYONE know where on earth one might find websites with simple javascript photo/optical calculators approximating currency converters, imperial/metric, language converters etc...? There are several times in a week when I'd love to get my hands on a simple calculator to crunch my 1/f=1/i+1/0 type formulas... to find a lens to project a print of max. size or to figure out what type of lens to shoot a given macro shot with - or to figure out if I can feasibly do a shot of the sun on 4x5, etc. etc. etc....

would be handy!! I've looked and looked on google, etc.. but to no avail.

Thanks
Jonathan

although it only does a small portion of what you list, I have used fCalc several times. Last time I downloaded it, it covered camera taking things like angle of view, DOF, etc

Hmmm...yes... I just did another google check to verify my result. oops! suddenly - calculators - so egg on my face!! Fcalc seems quite promising - though I can't get it to update it's results on my computer. So I wrote the author about it. I'm on system IX - so it really shouldn't be a problem... we'll see.