I have always thought that search engines such as Google find new content only when they crawl the Web. When I've added content to other websites I've maintained, it usually takes from days to weeks to show up in a search engine like Google.
But I've noticed that as soon as I post stuff to my WordPress blog, I can find it indexed in Google. It looks like a preliminary index entry, since it does not show a link to a cached copy of my new post for a day or two, although I can click on Google's results to get to my new post right away.
So the question is...
Does WordPress (or other blogs/websites) have a mechanism they employ to advise Google (or other search engines) that a new post has been added to a site? (and if so, does WordPress indeed do this?)