The first four links below are provided by The People`s Government of Guangzhou Municipality dated 2005
This appears to be the best all round information on Entry Exit Regulations.

Items Forbidden for Entry into China
http://www.gz.gov.cn/vfs/subsite/QFZZQNCH-UEYR-RYE4-CQEP-PO0PXEO7LORY/content/content.jsp?contentId=260961&catId=3194

Items Forbidden to exit China
http://www.gz.gov.cn/vfs/subsite/QFZZQNCH-UEYR-RYE4-CQEP-PO0PXEO7LORY/content/content.jsp?contentId=260960&catId=3194

Customs Measures and Import Duties on Personal Baggage
http://english.gz.gov.cn/vfs/subsite/QFZZQNCH-UEYR-RYE4-CQEP-PO0PXEO7LORY/content/content.jsp?contentId=260240&catId=3192

Entry and Exit Visa Info + more
http://www.gz.gov.cn/vfs/subsite/QFZZQNCH-UEYR-RYE4-CQEP-PO0PXEO7LORY/category/category.jsp?catId=3194

Interim Provisions on Import Taxes on Articles Taken Into China by Foreigners Permanently Residing in China
http://www.china.org.cn/living_in_china/visa_customs/2006-10/19/content_1184938.htm

Information for those entering Hong Kong.
http://www.customs.gov.hk/eng/advice_advice_e.html

Another source of Information - American I think. The last update on the site was in late 2007.
http://www.chinaadviser.com/customs.html

If anyone has more related or up to date information please let me know.
Any questions please use the 'Ask Answer Experiences' section.