Developerworks have made an overview of the top 15 DW WebSphere articles of 2009, found this compilation from the Top 100 of 2009: developerWorks articles (and other favorite things) compilation. Lots of interesting stuff if you are in to stuff not only related just to IBM HW/SW, but also pure Java.
I just spent five minutes reading the article written by Tom Alcott The WebSphere Contrarian: Less might be more when tuning WebSphere Application Server
Aggressive tuning doesn’t always equate with improved application performance. This installment of The WebSphere® Contrarian discusses why this is the case and provides some high level performance tuning guidance.
Recommend reading that article, and then really dive into the details with selecting one of the top 15 articles: Case study: Tuning WebSphere Application Server V7 for performance