Jachty
Jachty. Page by Primoz Peterlin with a main emphasis is on ISO 8859-2. It contains also a lot of useful links for Central and East European languages.
http://www.stocznia-jachtowa.biz.pl/jachty.htm

Code 2000
James Kass Unicode shareware font. Code 2001 (supporting Plane 1) is also available as a beta.
http://home.att.net/~jameskass/index.htm

Agfa Monotype [This link generated an error during the last automatic check]
Agfa Monotype supplies a very comprehensive catalog of Latin and Non-Latin fonts. You'll find also on the site some informational material on the various scripts.
http://www.agfamonotype.com/software/

Cyrillic (Russian): instructions for Windows and Internet
Instructions for a non-Russian Windows: Cyrillic fonts included into Windows, standard and phonetic (transliterated) Russian keyboard layout, how to tune-up browsers/Mail/News software - Netscape and Internet Explorer/Outlook Express; Cyrillic in Unicode-based programs (MS Word, IE/OE)
http://ourworld.compuserve.com/homepages/paulgor/

Dmoz.org: Multiscript fonts section
The open directory has a dedicated section for multiscripts fonts. You might also check the fonts/foreign section for language specific fonts.
http://dmoz.org/Computers/Software/Fonts/Multiscript_Fonts/

FAIRY (Font savvy web server)
FAIRY is a font savvy web server that enabled modern browsers to efficiently show text correctly, with regards to used languages and fonts. Supported browsers include IE, Navigator and Opera on Windows and Macintosh. Supported languages include Latin, CJK, bidirectional and other complex scripts. Supported font formats include bitmap, Type1, TrueType and OpenType.
http://www.em2-solutions.com/apps/fairy/fairy.htm

Indian Language Fonts
Collection of fonts to support the various Indian Languages.
http://www.epatra.com/help_dfont.html

Multilingual Unicode TrueType Fonts in the Internet
Links to multilingual UNICODE TrueType fonts for Windows 95, 98, 2000 and NT. With the font server xfsft or in other programs supporting Unicode TTF's (e.g. yudit) they may be used in Linux and other Unix systems. This collection has been gathered by Christoph Singer.
http://www.ccss.de/slovo/unifonts.htm

OpenType mailing list
Open discussion group for technical issues specific to building and using OpenType fonts. It has a moderate traffic and the list archive is available on-line.
http://www.topica.com/lists/opentype

Unicode fonts and tools for X11
Markus Kuhn offers X Window System bitmap fonts for ISO 10646-1/Unicode. The fonts are freely available with installation instructions and example UTF-8 text files.
http://www.cl.cam.ac.uk/~mgk25/ucs-fonts.html