I read a very interesting article by someone who works for Yahoo about how he wrote a basic search engine in Ruby in just a few files. I wouldn't use this for a production system for as an example of how search engines work its fascinating and I plan to keep following his site to see how he enhances it

Description: http://blog.saush.com/2009/03/write-an-internet-search-engine-with-200-lines-of-ruby-code/

Source: http://github.com/sausheong/saushengine

... and he's got a really cool css/javascript formatter for the source in his blog. I've gotta learn more about SyntaxHighlighter