EAI stands for Enterprise App Integration. As you mentioned, there are lots of tools to do the job provided by different vendors. The main thing worth knowing is that there are no standards in this area yet. Hence it boils down to learning tools from proprietary vendors. It again comes down to how quickly you can learn and adapt. Some of the EAI tools widely used are MQSeries, IBM Msg broker, TIBCO, Webmethods.
Forgot to mention one important fact. EAI fetches you more money as compared to any other conventional programming job (
j2ee, .net).
Hope that helps.
[ July 14, 2006: Message edited by: jay shankar ]