A year ago you had to wait days if not weeks to see your content indexed by Google. Now many web pages are indexed in 5-10 minutes. At least that's the case for many blog homepages, which are updated in almost real time. Here you can see the homepage of a PageRank 4 blog:
...and here's the proof that the blog post was created 11 minutes earlier (the result is from Google Blog Search):
Google could use the ping feature of the blog search engine to get notifications when a site is updated. This doesn't work for all the blogs, so there may still be a prioritization algorithm.
Update (less than half an hour later):
More Data on Privacy, but Picture Is No Clearer
6 minutes ago