Been battling for a while getting Eclipse WST (Web Standard Tools) and WTP (Web Tools Platform) to run on Eclipse 3.0. Eventually gave up on it and installed 3.1. It's a monster download and you need to add the optional WTP plugin.
The software updates feature under Help makes it a snap. Remember to click the “Select Required” button to enable the features required by WTP which are not already installed. Got it all installed and now can right-click on a WSDL file and select “Validate WSDL”.