One hears such sounds, and what can one say but... (Music Question)

[Sunlight]

I was listening to some music on the showcase thread (awesome music, by the way), and I had this feeling I haven't had in ages. Basically I want to try getting into music. I have some past experience with the piano, but I just want to try hooking up a keyboard to my computer and see what I can come up with.
I was wondering if anyone could give me some advice on what kind of keyboard to get, and what kind of software to use? I do realize that the tool doesn't make the craftsman, but I just want to make sure I don't end up buying something completely worthless.