Websites: xdot, xdoubledot symbols?

If you are in the sciences, you should be using LaTeX to typeset your papers. Much better layout and you get all the symbols you need.

check it out, \dot{x} gives you xdot, and \ddot{x} gets you xdoubledot

It also makes bibliography management and citation insertion super easy.

if you are a super noob to it, you can use LyX: http://www.home.zonnet.nl/rareitsma/lyx/ [Broken]

as for word, I dunno. don't use it for writing.

 

[tex] \dot{x} \ddot{x} \dot{y} [/tex]

 

LaTeX......

 

If you're working with letters that are vowels, you could just use standard diacritical marks, otherwise I have to agree with the concensus that LaTeX is best.