I lived in China for 2 years, so I will share what little I know.
TaoBao - Whenever we wanted to buy anything (and I mean anything) the first place we would look is on taobao. People talk about it as a Chinese eBay, but I didn't see the auction format, so I would say it is more like Amazon, but with more stuff possibly. I have no experience of them sending to another country, but within China, this is the daddy.
AliBaba - Whenever we needed bulk orders of something, we would go to Alibaba. I worked with a bar, a guest house and a restaurant, and if we needed something like a complete set of garden furniture, Alibaba was the place to go. Again, no experience of ordering from another country, but this is now a huge international company. Within China these are the big boys. I have also heard that if you have ideas about your own products you want manufactured (even counterfeit) this is a good place to start looking for a manufacturer. Alibaba is just a directory of manufacturers, so you need to really do your research and find respectable dealers and manufacturers to work with.
DealExtreme - I was racking my brains trying to think of the name of this Hong Kong company, but then WormWH mentioned it in his reply above. My brother and my friend worked a lot with these in the past and never had any problems. They sell gadgets and imitation goods, and are very reliable. My brother and my friend made $$$ with imitation Dr Dre Beats Headphones when they came out, and the quality of the product and service from deal extreme was excellent.
Hope this helps. Best of luck.