All Google Fonts are open source and are without cost

This website is a curated collection of typefaces that are available under a variety of free licences somewhere on the interwebs.

Fontshare is a free fonts service launched by the Indian Type Foundry (ITF).

Test drive programming fonts online: the definitive list of fonts for code.

The Miao3.cn website offers a comprehensive library of Chinese and English fonts for online preview and free download, with a vast collection of 1192 free commercial-use fonts and a feature allowing users to submit fonts.