JSP and Servlets are a very common choice for serving dynamic web content. Just look at how often your browser calls a page with the JSP extension. Servlets (JSP is compiled into servlets) are faster than CGI in most situations, or so I have heard. Java web apps are very well supported by the likes of IBM and ORACLE and so are very popular at big corporate websites. A lot of smaller organizations' websites (often created by outsourcing/consulting firms) use them as well.
As for personal sites, CGI languages have been more popular. Methinks this is because Java is not nearly as popular in the "hacker" community as Python, Perl and the like. Java is not fully "free" as in "free speech" - it does not come with a fully open source licence. People who build websites with dynamic content for personal use tend to support open-source, and so tend to favor the more open CGI languages. This is probably the main reason not as many personal websites and free servers use server side Java as use other options, even though JAVA is superior to CGI in many respects.
ASP is a bit easier to use (or so I have heard, I havn't tried it) than Servlets or even JSP, and is compatible with Microsoft technologies. Companies whose inhouse expertise primarily in Microsoft tech (and that is a LOT of companies) like to use ASP to the exclusion of Java in most instances when they do their own websites. This is the main reason that Java has not taken over the corporate word.
IN SHORT.... CGI still dominates the hacker/personal world. Java and ASP fight for the business market. ASP tends to have an edge in smaller and/or Microsoft centric shops. JSP/Servlets has an edge in larger shops and in places where alternatives to Microsoft are used - especially alternatives provided by large Microsoft competitors like IBM and Oracle. But this is just a gross generalization. There are many, many exceptions.
