Question: How do I data mine a pile of text to get keywords by usage? ("Jacob Smith" or "fence")

And is there a software to do this already? even semi-automatically, and if it can filter out simple words like "the", "and", "or", then I could get to the topics quicker.

Answer: 
There is also a service called [Alchemy](http://www.alchemyapi.com/) that can do term-extraction, concept tagging, sentiment analysis and so on.

It's valid, I tested it but I don't know they commercial policies (if any).
They provide APIs for any sort of language (pretty much).

I read somewhere (sorry I don't remember where anymore) that the output given by Alchemy is less noisy compared to those proposed by Joseph.
I personally recommend Maui (<http://code.google.com/p/maui-indexer/>): it relies on KeA but extends it in a variety of ways. It is trainable and can use RDF formatted terminologies.