There are many books that cover this topic but one of the newest books that covers portals and portlets is Portlets in Action by Ashish Sarin. The book is so new it actually hasn't been published yet , but you can preview it through Manning's Early Access Program (http://www.manning.com/sarin/).
Thanks for your reply..
I will be working on Liferay portal...
Joined: Mar 30, 2005
If you're working with Liferay, then be sure to create an account on Liferay.com. From there you can explore the Liferay Community Wiki which is a great resource to get started. The wiki is community driven so as you're getting familiar with Liferay feel free to enhance any of the articles you find. On the Liferay.com site you'll also find the Message Boards and additional Documentation.
I would also recommend that you take a look at Liferay in Action by Rich Sezov. The book has not been published yet, but it is currently available through the Manning Early Access Program (MEAP) and you can download the first chapter for free to get a feel for it. Check out Rich's Blog to keep up to day on publishing details.
Thanks once again Jeff, I have already created an account in Liferay.com, yes, infact there are lot of good articles on liferay wiki, for new users to get started up. The book Liferay in Action by Rich Sezov seems very promising.. Will keep checking the Rich's blog, for further details of book.. Thanks, once again, for your assistance on getting started up in portal..