Richard Semper

THE place to go for free soundfonts - large library, many contributors.

Large collection of free soundfonts and other software. See their article ‘How to build a bank of soundfonts’. Registration required for downloads.

Offers collections for sale, some free soundfonts available.

Shareware Music Machine. SoundFonts, editors, players, and utilities.

There are many sites offering large libraries of both free and paid for soundfonts for download.
I am including links to the main ones here, along with links to further sites which give more information
and insight on the subject. Note that as I write (summer 2011) many sites are outdated and links to some
sites no longer work properly. The ones below I have checked to ensure they are still current.