Quoting Paul Lutus <nospam / nosite.zzz>:

> I hope for an eventual decent open-source symbolic math processor. There was
> one (the name of which escapes me at the moment), but it is presently
> abandonware.

The only one that is more or less abandoned that I recall is MuPAD, and that was
abandoned by the community because the developer refused to open the package up.
The base version is/was free as in beer but the full version was free in neither
sense.

Axiom is decidedly active; check out

http://wiki.axiom-developer.org/FrontPage

and

http://portal.axiom-developer.org/

> I am personally spoiled by Mathematica, and, not being a particularly
> skilled mathematician, perhaps to a fault.

Depending on the type of physicist you are, there are quite a few open-source
specialty packages. And while not strictly open source, if you're a teacher or
a student, you can usually get software on an "academic license". It's free to
other academics but they expect industrial users to pay for it. In my area,
computer performance modeling, there is a lot of "academic-licensed" software
but only a few good ones are truly open source. Which is why I went down the
Ruby path in the first place for Rameau.

http://rubyforge.org/cgi-bin/viewvc.cgi/Rameau/?root=cougar

> I wouldn't have guessed musical notation without help, but I agree, it meets
> the definition, and, until the invention of the car radio, it was more
> widely used than mathematical notation. :)

Actually, just about every middle class home in America had a piano before radio
and the phonograph. I think there are still a lot more people who can read music
than there are who can read a PDE textbook. :)