How and how much are the protests in Hong Kong being reported or talked about inside China?
First of all, searching mainland newspaper pages today for the keyword “Occupy Central” we find around 20 Chinese newspapers that have run an official Xinhua News Agency release filed yesterday evening, September 28. That article is a direct report of a statement highly critical of “the illegal gathering ‘Occupy Central'” issued yesterday by the Hong Kong and Macao Affairs Office of the State Council.
Aside from use of this official Xinhua News Agency release — deep in the inside pages in all cases — we have only the example of the Chinese-language edition of the Global Times, which has a prominent front page piece with a jump to page 16. That article begins:

In what direction will Hong Kong be led? The violent clashes that played out yesterday on the streets in the vicinity of Hong Kong’s center of government are a cause of concern for all who care about Hong Kong’s future.
香港究竟要被引向何方？昨天，香港政府总部附近街区上演的暴力冲突让所有关心香港前途的人忧心忡忡。

At present, it seems that outside this highly restricted coverage in the news pages we have only the same highly restricted coverage on news portal sites. If we found coverage on major news sites in China, we would expect it to be 1) the Xinhua release on the above-mentioned Hong Kong and Macao Affairs Office statement, 2) information from the address given by Chief Executive C.Y. Leung at 1AM today or 3) shares of Global Times material.
As of mid-day, most major news sites had no prominently placed coverage at all. That includes the Xinhua News Agency website, People’s Daily Online, Sina.com (China), Sohu.com and QQ.com. However, when you select “news” on the home pages of the above-mentioned commercial sites, both Sina and QQ offer the Xinhua version of the already-very-outdated remarks made by Chief Executive C.Y. Leung yesterday, September 28.
The “coverage” on the QQ News site differs from other commercial sites in prominence of treatment. It uses a slightly larger headline, and also links to an August piece in the official People’s Daily addressing Occupy Central.

Searching news sites inside China for any coverage at all of what is happening in Hong Kong, the most current information mainland readers are likely to find is the full text of C.Y. Leung’s 1AM address on the ongoing protests. That information is being relayed by China’s second official news agency, China News Service.
So what about social media?
We encourage readers to use our WeiboScope tool for updates on deleted posts about Hong Kong and other issues in China. But it is clear that there is a flurry of activity about Hong Kong on Sina Weibo. As we would expect, posts about protests in Hong Kong are disappearing almost as quickly as they appear.
A search of “Hong Kong” on Weibo returns mostly entertainment, finance and tourism related results, with odd scattered results including mention of the protests, even some using the Chinese term for “Occupy Central” (占中). Generally, however, when you click into the posts about events in Hong Kong right now, you find the posts are already gone, yielding Sina’s “Sorry” message.
The surest way to get posts through related to the Hong Kong protests at all seems to be stick to the Global Times front page (like this post), its bold headline reading: “Hong Kong Government Fiercely Rejects Illegal ‘Occupy Central.'”

Interestingly, as I was testing search terms on Sina Weibo a few hours ago, a little pop-up window came up in the bottom right-hand corner of Weibo directing me to the China News Service report including the full text of Leung’s remarks at 1AM today.

Here is a brief taste of posts deleted today from Sina Weibo. Note that even posts, like the last one, that are critical of the protesters are being removed.
(1)

From User “kingsouleater00th”
With more than 3,900 fans
“Today’s front page in the Apple Daily“
苹果日报今日头版

(2)

From filmmaker Xu Xin (徐辛XuXin)
With just under 13,000 fans
“microphone”
[話筒]

(3)

From User “Reporting Hong Kong” (報道香港)
With more than 11,000 fans
“So violent like this, and you tell me you want democracy. I don’t want this kind of democracy!”
你們如此暴力，和我說是爭取民主，這樣的民主我不要!