I know from experience that there are tons of different soundfonts to be found on the net.
I recently came across a killer soundfont library.

It´s a package of orchestral instruments. You are probably just saying, "- same old crap!"
and usually you would be right, but not about this package. I was surprised hearing the amount of quality it had and the way they´ve managed to capture every instruments expressions.

This library contains everything from string sections to brass and woodwind sections.
It also contains a percussion section and a chromatic percussion section. Even a couple of REALLY good choir fonts.

I use this library often, almost everytime i am working on a new piece.
If you want to make something light-weight i´d strongly reccomend this library.

This library is put together by a guy named Mattias Westlund, so i have nothing to do with it. I´m just sharing =)

Link to site containing download-link
http://sso.mattiaswestlund.net/index.html

If you want just a few of the different instrument sections, but can´t be arsed to download the whole file, just give me a pm and i´ll send you the section you want to your e-mail.

(Remeber! This is a library of soundfonts. You´ll need a soundfont player in order to be able to use these.)

Probably the best free soundfont player
http://www.cakewalk.com/Download/sfz.aspx