I've found facebook ads extremely effective, for very low cost. I started using them because I noticed that the ads that I get are a good match for my interest. Go for the more expensive option of per click (ie you pay for those who click on your ad) rather than per view (you pay each time it's displayed to someone, whether they click or not).
We are spending around $100 HK (not US) per week on FB advertising.
It's best to link this to a facebook fanpage for your company / product.
On google / yahoo if you are targetting local chinese speaking audience yahoo is the one to go for.