list of Open source resources + projects:

http://www.sourceforge.net/
http://www.freshmeat.net/
http://www.jboss.org/
http://www.jdom.org/
http://www.dom4j.org/
http://www.openejb.org/
http://www.openjms.org/
http://mx4j.sourceforge.net/
http://www.castor.org/
Apache Software Foundation:
http://www.apache.org/
Apache web server (HTTP server):
http://httpd.apache.org/
http://www.apache-ssl.org/
http://jakarta.apache.org/tomcat/index.html
http://jakarta.apache.org/
http://xml.apache.org/
http://www.mozilla.org/
http://www.mozdev.org/
http://www.aolserver.com/
http://www.enhydra.org/
http://www.exolab.org/
http://www.jxta.org/
http://www.jini.org/
http://www.freebsd.org/
http://www.netbsd.org/
http://www.openbsd.org/
http://www.kernel.org/ (Linux kernel)
http://www.debian.org/
http://www.gnu.org/
http://gcc.gnu.org/
http://savannah.gnu.org/
http://www.opensource.org/
http://www.tigris.org/
http://www.collab.net/
http://www.junit.org/
http://www.httpunit.org/
http://www.3glab.org/
http://www.amberarcher.org/
http://www.gnuenterprise.org/
http://www.netbeans.org/
http://www.eclipse.org/
Mono project:
http://www.go-mono.net/
http://www.dotgnu.org/
http://www.python.org/
http://www.perl.com/
Comprehensive Perl Archive Network:
http://www.cpan.org/
http://opensource.go.com/
http://www.opensource.apple.com/ - includes Darwin project
IBM open source projects:
http://www.ibm.com/developerworks/oss/
http://www.openadaptor.org/
http://www.objectweb.org/
OpenSymphony:
http://www.opensymphony.com/
Open For Business project:
http://www.ofbiz.org/
http://opensource.compaq.com/
http://www.opennms.org/
http://www.jabber.org/ - instant messaging (chat) software
http://www.openldap.org/
http://www.sunsource.net/
http://www.e-speak.net/
http://www.gtk.org/
http://www.gnome.org/
http://www.kde.org/
http://www.koffice.org/
AbiWord word processor:
http://www.abisource.com/
http://www.openoffice.org/
http://www.gimp.org/
MySQL database:
http://www.mysql.org/
http://www.us.postgresql.org/
http://firebird.sourceforge.net/
http://www.sapdb.org/
http://www.dbxml.org/
http://www.xmlblaster.org/
Jetty (Java HTTP Servlet server):
http://jetty.mortbay.com/
Jigsaw (HTTP server, written in Java):
http://www.w3.org/Jigsaw/
Open source SyncML server:
http://sync4j.sourceforge.net/
Common Data Security Architecture (CDSA):
http://sourceforge.net/projects/cdsa/
http://www.saxproject.org/
http://www.php.net/
http://www.zope.org/
http://www.webmacro.org/
http://www.cygwin.com/
http://www.cvshome.org/
http://www.openssl.org/
http://www.openssh.org/
http://www.stunnel.org/
http://www.winehq.com/
http://www.aspectj.org/
Compiere (open source ERP and CRM):
http://www.compiere.org/
http://www.samba.org/
http://www.xfree86.org/
http://www.sendmail.org/
http://www.qmail.org/
http://www.postfix.org/
http://www.isc.org/products/BIND/ - from the Internet Software Consortium
( http://www.isc.org/ )
http://www.isc.org/products/DHCP/
Web proxy cache:
http://www.squid-cache.org/
http://www.gnupg.org/
http://www.antlr.org/
http://www.sablecc.org/
http://www.doxygen.org/ - documentation system (like Javadoc)
Java PDF library:
http://www.lowagie.com/iText/
Java Excel library:
http://jakarta.apache.org/poi/
http://developer.arsdigita.com/acs-java/
http://www.cups.org/
http://www.argouml.org/
http://www.xbeans.org/
http://www.vim.org/
Open source projects at SGI:
http://oss.sgi.com/
http://www.onlamp.com/
Open Source Development Network (OSDN):
http://www.osdn.com/
http://sources.redhat.com/
http://www.ximian.com/
OpenUSS project:
http://openuss.sourceforge.net/openuss/index.html
HP ChaiServer:
http://devnet.hp.com/projects/csopen/
HP MicroChaiVM:
http://devnet.hp.com/projects/microchaivm/
HP Chai Appliance Platform:
http://devnet.hp.com/projects/chaiplatform/
http://www.xwt.org/
http://www.freedos.org/
http://www.libpng.org/
http://www.gzip.org/
http://www.info-zip.org/
Open Source Development Lab:
http://www.osdlab.com/
http://www.devshed.com/
http://www.parlay.org/
http://www.boost.org/
http://tuxedo.org/~esr/writings/cathedral-bazaar/
http://tuxedo.org/~esr/writings/homesteading/