Suggestion 1
You could apply an inline style....apply the "Font" attribute. Right click
the text area, go to Styles > font.... etc. That's to change it to *one*
font.
I don't know about multiple fonts in the normal course of textareas with in
a form.
Suggestion 2
There are editors around that make use of a textarea box where you can apply
different fonts and other text attributes, but these are integrated into
applications like content management systems or a blogs or
discussion/bulletin boards or whatever.
This is the one I mean:
http://www.htmlarea.com/ but I don't know if it is
what your specifically after - it's one of many editors around, but it is an
editor; not just for displaying text in a textarea.
The above editor is integrated into this Blog system "SimpleBlog"
http://www.8pixel.net
However this is "a major script" as you said you didn't want.
My first suggestion is all I can think of; unless other members of this
group can come up with another solution.