Mac and Win formats available. Emigre Home of the popular Emigre magazine. Commercial fonts galore. All formats available, excellent quality. Eyesaw - Freeware site with some good designs.
Quality is good but the character sets are limited.
Fontalicious - Ben Balvanz is the designer at this site and is well known for his adorable freeware fonts. Good character sets. Mac and Win formats available. Font Bureau Home of some of the best commercial fonts. They have every style of font imaginable.