You could just use regular JSP syntax:
<%
String someVar = "";
%>
<title><%= someVar %></title>
or, with the
struts tags, you can store your titles in a properties file and use the message tage in the struts-bean tld.
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html:html locale="true">
<head>
<html:base />
<title><bean:message key="some.page.title"/></title>