This week's book giveaways are in the Refactoring and Agile forums. We're giving away four copies each of Re-engineering Legacy Software and Docker in Action and have the authors on-line! See this thread and this one for details.
You can think of portlets as mini application windows existing cohesively on a page.
One real life example of a portlet is iGoogle which allows you to customize your page with "widgets" These widgets are the portlets