Brad Appleton's Tutorial
http://www.enteract.com/~bradapp/docs/patterns-intro.html

Douglas Schmidt has a great amount of Pattern Material especially on Real-Time Patterns http://www.cs.wustl.edu/~schmidt/patterns.html
... and his book
http://www.cs.wustl.edu/~schmidt/POSA/

Christopher Alexander architectural site... devoted to rebuilding the earth. Includes his daily column. Alexander's design patterns are for homes and buildings.
http://www.patternlanguage.com/

Christopher Alexander: An Introduction for Object-Oriented Designers
http://gee.cs.oswego.edu/dl/ca/ca/ca.html

Good links to other pattern sites
http://www.agcs.com/supportv2/techpapers/patterns/othersources.htm

Here is one of the most popular design patterns site
http://hillside.net/patterns/

Design Patterns for Real-Time Software - A paper presented at the Embedded Systems Conference West, Sep 1996, San Jose, CA.
http://www.objectime.com/otl/products/patterns.html

Java and Design Patterns
http://www.javasuccess.com/

Java and Serverside Design Patterns
http://www2.theserverside.com/patterns/index.jsp

Frameworks and Design Patterns
http://fram.nrsc.no/~anita/Ownpubl/Tapos/mfw_paper1.4.htm

C++ and Think in Design Patterns
http://www.ccs.neu.edu/home/futrelle/teaching/com1101w2001/eckels/ticppv2-web/Chapter10.html

A Pattern Language for Relational Databases and Smalltalk
http://www.ksc.com/article2.htm

Design Process Patterns
http://www.ambysoft.com/processPatternsPage.html#Online%20Process%20Pattern%20Resources


Main Sun site J2EE Patterns:
http://developer.java.sun.com/developer/technicalArticles/J2EE/patterns/

Restricted to registered developers at the Sun site.
http://developer.java.sun.com/developer/restricted/patterns/J2EEPatternsAtAGlance.html

The Sun Pet Store Reference Application
http://java.sun.com/j2ee/blueprints/jps11/archoverview.html
... and a related article
http://java.sun.com/features/2001/05/petstore.html?frontpage-headlinesfeatures


OSS Through Java Initiative (OSS/J) Specifications available at the following link.
http://java.sun.com/products/oss/

Companies the OSS/J - Quality of Service API
http://java.sun.com/aboutJava/communityprocess/review/jsr090/

Companies in the OSS/J - Service Activation
http://java.sun.com/aboutJava/communityprocess/review/jsr089/

Companies in the OSS/J - Trouble Ticket
http://java.sun.com/aboutJava/communityprocess/review/jsr091/

The Java community process:
http://java.sun.com/aboutJava/communityprocess/jsr/jsr_099_jspa.html


Some related articles:

Good article on BEA and future products.
"[BEA] has a real track record when it comes to standards," as evidenced by its push for J2EE and BTP, said Peter O'Kelly, an analyst at Patricia Seybold Group.
http://iwsun4.infoworld.com/articles/hn/xml/01/05/29/010529hnbea.xml?0530weam

This new application server is IBM's first server software product to include support for the J2EE (Java 2 Enterprise Edition) platform. It also supports a variety of open standards such as XML, UDDI, SOAP (Simple Object Access Protocol), and EJB (Enterprise JavaBeans), an architecture for building reusable applications deployed from a server to an entire network.
http://iwsun4.infoworld.com/articles/hn/xml/01/05/30/010530hnwebsphere.xml?0531thap

BEA has a good University program, 6 month free license and several other benefits. You can try this link, but you may need to register under the developers web page first.
http://developer.bea.com/programs/university.jsp

There are 9 fully J2EE compliant application servers.
http://www.mgm-edv.de/ejbsig/archive/news/newu_01_17_a.html

Here are the links to most of application servers. Some are more J2EE compliant than others.
http://www.mgm-edv.de/ejbsig/ejbservers_tabled.html

Enhydra is a popular open source J2EE application server but is not "fully compliant"
http://enterprise.enhydra.org/software/downloads/cuts/4.0-beta1/index.html

A very informative tutorial on the application server market
http://serverwatch.internet.com/articles/appsmkt/index.html

Article on embedded systems and complexity
http://java.sun.com/features/2001/05/embeddedsys.html?frontpage-headlinesfeatures