Arachno by Maxime Abbey	This bank includes many famous sounds from the best synthesizers by Roland (D-50, Sound Canvas...), Korg (M1, X5...), Yamaha (MU, Clavinova...), Fairlight (CMI), E-MU (Emulator), Ensoniq, and many others.
Titanic 1.2	Go here for two larger and high quality SoundFonts: Chorium and Titanic.
Giant SoundFont	Giant Soundfont 5.5: Note that you will need to download banks 1, 2, and 3 of v5.5 as well as the drumkit which is labelled v3.0. Giant soundfont is 450 MB uncompressed, the author updates it regularly.
Sonatina Symphonic Orchestra	The creative commons-licensed orchestral sample library Sonatina Symphonic Orchestra is a free library by Mattias Westlund in SFZ ("SoundFez") format. Sounds good!
Free Orchestral SoundFonts	"Free soundfont files for download. Brought to you by the Wesnoth Music Dev team. " - A decent collection of public domain SoundFonts, I would say. Have a look.
Free Sound Vault	"Here you can download free sound samples, soundfonts, wavs, hip hop samples, etc. for your use in music production and hip hop beat making."
Soni Musicae	"Original good quality soundbanks, in different formats, mainly harpsichords and pipe organs"
Precisionsound	"High quality sound samples for music production and sound effects for the multimedia/movie industry" Various formats
Soundfont Click	New site by the people behind the Composition Contest site (se below). Get the free Merlin SoundFonts here!
Papelmedia	There are a few good free SoundFonts there. And some very good commercial ones.
Jensen Samples	Authentic guitar sounds. Some free SoundFont demos. By Andreas Lundsfryd Jensen.
SGM 180, Crisis 1.8	Two good large General Midi SoundFonts
MIDISOFT	Some 14 free SoundFonts
NTONYX	Some 17 free SoundFonts
Free guitar soundfonts	by Andreas Lundsfryd Jensen
Sf2-files	Free and commercial hi-end quality soundfonts in many formats
Pipe Organs	Bruce Miles' 'English Organ' (Classical) and 'Cinema Organ' (Theatre)
Composition Contest	Some pretty good ones, e.g. the Merlin GM is a must. This site was previously known as "Midi Contest"
Giga files	Some free files in both GIGA and SF2 format
Hammersound	A classic place to go.
HYBRID	No SoundFonts to download. You can buy a collection on CDs.
Sf2 midi download	Quite large selection. Have a look.
Personalcopy	Smaller number of files but good quality. (Here you can find the old SFPack program.)
S Christian Collins	GeneralUser GS is a very good GM and GS compatible SoundFont
Nando Florestan	Some very good orchestral SF's
SoundFonts.it	Don't go to the new site for SoundFonts, look in the old one.
Analoquesque	Not too many freebies.
MelodyMachine	Here youi can find the sfArk compression utility. And some non-GM soundfonts.
Lysator	This is a Swedish FTP server with mostly old stuff.
SynthZone	Soundfont Resources, lots of links
Melodik	Rather large list. Site is in Turkish language only.
TheJazzPage	Well, eh... The Jazz Page
Johannes Roussel's site	Some good stuff there
SONiVOX (Sonic Implants)	Not so many free Soundfonts to download
HomeMusician	Download and post free soundfonts, MIDI files, tabs, gear reviews
Sf2 (Russian site)	Seems to be a large collection?
Helgesson	The Maestro Concert Grand by Mats Helgesson
Shareware Music Machine	Here you will not only find a collection of SoundFonts, but also SoundFont editors, players, and utilities.
RKHive SoundFonts	... a SoundFont archive since 1995. Here you can find some of the classic GM SoundFonts (in "Banks").
Ethan Winer's originals	Ethan provides a set of original musical instruments
Allanah's collection	A large collection - listed alphabetically on the right hand side as you scroll down a bit - from other locations on the Internet, some of them now long gone.