There are some 275 million blogs hosted on Blogger.com and all them have possibly been blocked in China.
This "crackdown" could have some relation to June 4, 2009, the day when the world will mark the 20th anniversary of the Tiananmen Square incident or it may even be a service disruption because Google is saying that they are "working to restore access to Blogger in China."
In either case, users have been unable to access Blogger inside China since May 17th.
Blogging on Blogger from China
If you are inside Mainland China and need to publish new entries on your blogger blog, you can use the "post by email" option of Blogger or something like Posterous – email your articles to email@example.com and they will auto-post the message to your blog. Online blog editors (like the one in Facebook) can also help you write entries in blogger from anywhere.
And here are some tricks to help you read blogger blogs inside China.