Main site of Creative, the developers of the Soundfont format. Has a number of informative tutorials on making and using Soundfonts. 

Good section of links to Soundfont Resources and Products.

Good article on experimenting with Soundfonts. (Requires registration.)

Information about SBLive!, Audigy, and other Creative soundcards.

sfz player is a free plug-in that can play Soundfonts in any application supporting the VST format.

Small company with affordable professional level audio editing, music sequencing, and sound production software.