J2EE Logging Service
While googling, I came across a draft chapter for an unnamed book (http://www.objectsource.com/j2eechapters/Ch06-Logging_Service.htm) that discusses the creation of a JMX controlled logging service based on Log4j.
NDC and MDC
http://wiki.apache.org/logging-log4j/NDCvsMDC
JMS Logging
Develop an Asynchronous Logging Framework using log4j with JMS and WebSphere MQ by Roland Barcia http://www-128.ibm.com/developerworks/websphere/library/techarticles/0207_barcia/barcia.html
Log4J appenders
List of 3rd party appenders: http://logging.apache.org/log4j/docs/download.html
LogWeb
LogWeb is a Struts-based interface for configuring log4j. It is released under the Apache license (like Struts) and would probably be a wise choice compared with rolling your own. I've used it, and it required a bit of hacking to make it fit nicely within the application. http://www.codeczar.com/products/logweb/index.html
Further Reading
While collecting information on this topic, I came across some other, related publications that might be of interest.
Patterns for Generation, Handling and Management of Errors by Andy Longshaw and Eoin Woods http://www.blueskyline.com/ErrorPatterns/A2-LongshawWoods6.pdf
Error Handling for Business Information Systems -- A Pattern Language by Klaus Renzel http://www.eso.org/~almamgr/AlmaAcs/Releases/ACS_4_1/Docs/ARCUSErrorHandling.pdf
A better FAQ for log4j than on the Apache site: http://www.slf4j.org/nlog4j/faq.html (At least, it includes details I’ve not read elsewhere.)
Understanding Classloaders: log4j in a J2EE Environment by Vikram Goyal http://www.onjava.com/pub/a/onjava/2003/04/02/log4j_ejb.html