There’s a good introduction to the new JSP expression language part of J2EE 1.4 in the Enterprise Java Technologies Technical Tips. I think the expression language is a really valuable addition to JSP’s, making jsp’s almost as easy to write as velocity pages.
If you’re not using a J2EE 1.4 compliant application server yet, you can use JSTL instead. It’s not as nice, as the expression language will only work inside JSTL tags, but it’s better than nothing. If you’re using Oracle’s 9iAS, be warned that you’ll need to upgrade oc4j to version 9.0.3, as JSTL’s expression language will not work on 9.0.2.2 and earlier. OC4J 9.0.2 is not J2EE version 1.3 compliant, version 9.0.3 is!