This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
As you've discovered, you can't nest tags like that--that's simply not valid JSP. You'd need to set the value to a variable and use either JSP 2+ EL, or the Struts EL tags if you're not running in a JSP 2+ container.