Personally, I would give a more conservative answer, it depends. If you are trying to get started with servlets (although, I wouldn't believe you) yes, Tomcat is enough. However, if you are in the process of serving servlets etc for a commercial purpose and with commercial support for static html pages, then you might need apache. Pl. note Apache supports static html pages and Tomcat supports servlets, JSPs and html pages. regds. - satya
Also Apache supports CGI, in-process perl, PHP, htaccess authentication, URL rewriting, SSL and a whole load of other modules. Many people use Apache for all these things, and a plugin (Tomcat, Resin, JRun etc.) for servlets and JSPs.
another comment abt apache..."apache is a reference implementation on windows". All these goodies are fully supported on Unix, but on windows there maybe some surprises. Atleast thats' what I understand from Apache documentation. In short, your OS also matters to a certain extent. Couldn't resist to say something negative.... regds. - satya