Like Brown Corpus for English: http://en.wikipedia.org/wiki/Brown_Corpus
For a big-data Chinese corpus, have a look at this one:
- A million-word level corpus
- Contact: Miss Su-Chu Lin (林素朱), firstname.lastname@example.org
- Introduction in Chinese
- Not sure if you can download it for free
I haven't found a large corpus, but I have used the results of some projects that analysed all Usenet newsgroups from 1993-1994. You could probably contact Shih-Kun Huang for information about the original corpus.
I don't know if they can be downloaded, but there are lots of example sentences on jukuu.com.
You can download all of the Chinese language Wikipedia. (you would probably want: zhwiki-latest-pages-meta-current.xml.bz2)
Another source that may or may not be suitable depending on the specific project is Project Gutenberg's collection of Chinese language books. The downside of this source is that most of them will be quite old.