> Does any of you know any freeware equation editor besides
> MathType and MathCast? I was wondering because I would like to
> replace it by freeware but I can't find anywhere nothing like
> it.
I can warmly recommend LaTeX, too (the already mentioned TeXMacs is
based on TeX/LaTeX). If you take the time to learn it, you'll be
producing professionally typeset mathematics easily.
A big open question is the format that you need. You need an
equation editor for what? To insert equations in Word? To generate
EPS files? ...