Started up jboss 6 CR1 in jbossweb-standalone (after some tweaking--needing jbas-8659-jboss-beans.xml) and got a working server up and running. Deployed a struts 1.3 WAR. Application deploys. When accessing a page with a c:forEach tag in it, the NoClassDefFoundError is thrown. We have jstl-1.1.2.jar within WEB-INF/lib (verified by listing the war libs below).

WEB-INF/lib/cachetag.jar
WEB-INF/lib/commons-beanutils-1.8.0.jar
WEB-INF/lib/commons-chain-1.2.jar
WEB-INF/lib/commons-digester-1.8.jar
WEB-INF/lib/commons-validator-1.3.1.jar
WEB-INF/lib/jakarta-oro.jar
WEB-INF/lib/jstl-1.1.2.jar
WEB-INF/lib/standard-1.0.6.jar
WEB-INF/lib/struts-core-1.3.10.jar
WEB-INF/lib/struts-el-1.3.10.jar
WEB-INF/lib/struts-extras-1.3.10.jar
WEB-INF/lib/struts-taglib-1.3.10.jar

If I put the jstl-1.1.2.jar in jbossweb-standalon/lib, restart the server and run the application, then the error doesn't happen.