WSAD IDE
I am sure there are great tools out there to handle specific tasks. But for a completely global IDE for XLST/HTML/JAVA/CSS the best tool I have found is WSAD from IBM. It is built off of the Eclipse open source software. WSAD takes the Eclipse software to a whole new level. If you have the money and would like one single tool to do everything then this is it. The other nice advantage is that it integrates very well with CVS. It does not currently work with Tomcat 5.x. Version 6.0 should be released by first quarter 2005.
I have been doing HTML and Java development since Java version 1_1_7. The best tool I have seen is WSAD. It is rock solid. The only tools that come close are Net Beans and JBuilder (I think that is its name. It is/was the Java development tool that Oracle made available). I know that WSAD is pricy but I would never develop without it. I use to work with a guy who does similar types of development. He will have 8+ windows open at all times in order to do his job. I have WSAD, a browser and sometimes windows explorer open. He has a tool for each and every job. Now his tools are free. But the time he waists and the errors that I see him make convinces me that WSAD or a tool with the same features is the best way to go.