Cheong Fatt Tze Mansion has been renovated in the last decade or so after years of neglect. It is a World Heritage Site, as is much of Georgetown. Since it's renovation and conversion into a hotel, tours are offered to visitors for a small fee.
Unfortunately, the owners of Cheong Fatt Tze do not allow photos inside (mostly so they can sell postcards and books at inflated prices). The tour itself was worthwhile because it traced the family history of the house as well as quite a bit of Chinese culture. It was the best explanation of Chinese culture that I received since arriving in China (it's too bad I had to travel to Malaysia to get it).
We also were told that there is still another Cheong Fatt Tze mansion in Taipu, Guangdong--not too far from Shenzhen. Jia and I have planned to take a weekend trip at some point to find it.