Two of the most renown JEE servers are JBoss (now under RedHat) and GlassFish (from Sun).
However, if your company is primarily using Weblogic at the corp level and you want to have a development environment, you can download it here, it comes with a free developer license (which allows up to 5 ip addresses) to perform your test and development.
Maybe it is due to my lack of knowledge of the server. I was unable to successfully create my own project using the easy start. The project was created using the wizard but failed to start. Also, I noted that the weblogic server (10.3 still uses Java 1.4 instead of Java 1.5 or Java 1.6) as used by the JBoss and Glassfish. Also, there was no easy way to start the server by itself.
I tried JBoss, starting and stopping is very simple. I have yet to try out Glassfish.
JBoss 4.2.x is JEE 5 able but not certified. JBoss 5.0 is JEE 5 certified. Glassfish and Weblogic also support JEE 5. All three servers are supported by NetBeans.