Does it seem odd to you that a software algorithm can be patented?

I was reading about the LZW data compression algorithm. This is the Wikipedia article. The algorithm itself is rather ingenious and I encourage you to read about it, but what struck me is that there is a section in the article on the patent for it. The patents have all expired, so feel free to use the algorithm.

What else can be patented? Can you get a patent (or maybe a copyright) for a dance move? What about a teaching method or aptitude test?