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Java applications (as opposed to applets, servlets, etc.) are plenty easy. Two major IDE's are free: Eclipse and NetBeans.
Java can be used for simple "Hello World" programs as well as very complex graphical and browser-based applications. It runs on nearly all platforms, including many PDA's and cellphones. It's ubiquitous in the enterprise, used by IBM, Oracle, and almost everyone else except Microsoft. It's a very marketable skill.
About the only downside I can think of is that the IDE's like lots of memory, 512MB minimum, and large displays.
Greg