[texhax] Units in technical writing

[Gordon Haverland]

Lately, I've been lazy and writing things like $3 mSv/a$ in LaTeX.  
And LaTeX ignores the space between the number and the unit.

I have no problems with numbers with units being in math italic, 
or even writing chemistry in math mode and having chemical 
formulae in math italic.  But if one is introducing units, the 
introduction often doesn't have numbers to it (W = J / s), and 
sometimes one forgets to put everything in math mode.

I'm in the habit of \usepackage{isotope} now.  Is there a similar 
package which allows for nicely typesetting values with units 
(possibly with error estimates)?

I hope everyone had a good Christmas.

-- 
Thanks.
Gord