First, let me start by apologizing for such a late reply, but I've been out of the country for the past few weeks.
Next, let me just say that I really appreciate your comments on the article. The best reward for writing these articles is just knowing that someone out there read them and liked them.
Finally, I wanted to reply to your question. I have to admit that I hadn't really looked into creating an installer for my Ruby/Tk scripts. For the most part I just save the script to a USB key or email it to myself to use it another computer. In other words, I have so far only developed Ruby/Tk apps for myself.
That said, I did find a couple of articles on the O'Reilly Network that may be of assistance to you. They can be found at the following addresses:
PackageMaker Pro Tips
Creating Easy-to-Deploy Unix Applications for OS X
I haven't really found any good open source applications to wrap Ruby/Tk apps yet, but I'll keep looking. In the meantime, I hope the articles I've pointed out above help a bit, and if I find out anything else of interest, I'll post it here.
Thanks again for the comments.