I would say the biggest advantage I have seen for choosing to use ASP, is that it is easy to learn, and has great syntax for making maintenance easy later.
ASP can be sort of described as VBA embedded in HTML. So if you know HTML, and have any experience at all in programming with VB, then you are a good way there already!
You embed code in your standard html files with the open tag <% and close tag %>
ie.
<HTML>
<BODY>
<% Response.Write "This is a demo" %>
</BODY>
</HTML>
All code inside <% and %> tags gets executed on the server, converted into html result then sent to the client for output.
The above example would display 'This is a demo' on a blank web page.
I learnt asp 3 years ago from a book, and within 6 months I was quite competent with it. If you are competent and dedicated enough you should find learning from a good book quite easy. I learnt from "Using Active Server Pages" by Scot Johnson, but there are many great books out there, and any would probably get you started.
Your alternatives to ASP are things like Perl, Cold Fusion etc, and as far as I'm concerned, ASP will give you just as much functionality, with half the syntax headaches that the rest give you
I say go for it and learn ASP. My only other recommendation is that you keep in mind that the new ASP.Net and VB.Net are out now, and provide much more functionality than its predecessors. Maybe learn a little ASP first, then with your Java OO knowledge, ASP.Net shouldn't be hard to pick up.
Good luck - and happy coding!
Brett Birkett B.Comp
Systems Analyst