While the Dead Librarian mostly looks for the South Carolina dead her own ancestors come from upstate NY. It has been a long time since I worked on my own genealogy so last year while attending the NGS conference in Raleigh I decided to join the NEGHS and take advantage of their specialized online databases.
A couple of weeks ago the NEGHS came to Hilton Head, SC and I "forced" myself to attend. Which finally brings me to the point of this post. One of the cool internet sites I learned about is Netronline. Netronline provides links to county real estate public records and is a research information portal for property information, deeds & mortgage copies, tax records, parcel maps, assessment records, and public records nationwide.
It did not list the online marriage license information available in Richland County or the death certifcate index at SCDHEC but I found it to be a very useful tool. Also, the information is not retrospective but I did use it to locate a living relative in Arizona via California.
I think you will find it to be an invaluable resource. Bookmark it!