One of my SEO experiments was with buying expired domains and use it for SEO purposes. I bought an expired domain late Dec 2005. Eventually the PR was dropped and it was out of google's index. I wasn't able to develop that domain and so it just stayed there doing nothing.

Early July just a few weeks ago, I finally found it indexed by google. Counting back the month from the time I bought the domain, it seems like google has a 6 month penalty imposed on expired domains. Since it was late Dec, the 6th month was the latter part of June. It took a few weeks more for google to crawl the site and index it.

I can't really say that all expired domains go through this 6 month penalty, but in this one domain's case, it did.

Anybody had similar experience on expired domains?