Useful Links at One Spot WebSphere Portal.

WebSphere Portal Press Books:

IBM WebSphere Portal Primer: Second Edition

Mastering IBM WebSphere Portal: Expert Guidance to Build and Deploy Portal Applications

Programming Portlets: From JSR 168 to IBM WebSphere Portal Extensions

JSR-168 Portlet Development Simplified, Second Edition: Learning How to Develop Effective, JSR-168, Portal Applications, Everything from the GenericPortlet to the Struts and JSF Apache Portlet Bridges

Exploring IBM Accelerators for WebSphere Portal


IBM WebSphere Portal Redbooks:

WebSphere Portal Version 6 Enterprise Scale Deployment Best Practices


IBM Lotus Wiki:

Managing WebSphere Portal 6.1 Environments


WebSphere Portal Family Wiki

IBM WebSphere Portal RedPapers:

WebSphere Portal Best Practices

IBM WebSphere Portal V6 Self Help Guide

IBM WebSphere Application Server V6.1 Security Handbook

IBM WebSphere Portal Infocenter:

IBM WebSphere Portal Version 6.1 Information Center

IBM WebSphere Portal Version 6.0 Information Center

Reference: http://webspherehelp.blogspot.com/2009/07/websphere-portal-books-redbooks.html

Themes and skins Development:

http://www.ibm.com/developerworks/websphere/library/techarticles/0804_barnes/0804_barnes.html?S_TACT=105AGX10&S_CMP=LP