1) Absolutely most companies use Unix
Box as server machines.
2) Java Web Server is out of scene, because Sun won't develop it any more. MIIS does not support server-side Java. It is good for some small companies.
3) In Canada, IBM Webspehre is very hot. I think Websphere, Weblogic , iPlanet, Gemstome and leading Application Server Products.
4) Weblogic 4.5.1 will be out of stage soon.
Weblogic Commerce Server is a good tool for you to learn EJB.
5) Few serious companies use Windows NT/2000 for servers.