When I attended the local genealogical society presentation on Google resources, there were basically two items I thought could have been covered, but weren't. As it was, the presentation was already full with explaining advanced searching techniques on the basic search engine, the image search, the patent search, the product search, Google Books, Google Maps, and Google Earth. All in 90 minutes.
However, if they didn't cover these two items I knew about, it was possible they didn't know, and possible others might not either. Google has a lot of different services and search engines, and they don't make it possible to search them all at once, so some of them can remain hidden to users.
As I mentioned in the previous post, Google's News Archives can yield interesting finds, and now I am going to talk about what used to be called Usenet and which is now Google Groups.
Usenet began in the 1980s as a collection of discussion groups, mostly for college students and staff on any topic the users decided they wanted to talk about. Anything without limitations. Whenever a quorum decided a new topic was needed, it was added.
A company called DejaNews began organizing the Usenet archives in the late 1990s, and Google bought them in 2001 and formed Google Groups. Google Groups serves as both an archive going back to 1981 and a continuation of all the discussion groups. (This has frightened many former college students who began to ask, "Everything I posted there is now available for potential employers - or my kids! - to read? Forever?" It is possible to remove one's old posts, though if anyone quoted what you said, only they can remove that post.
A few of the groups that might be of of obvious interest to genealogists and family historians: Alt.Obituaries, and two dozen groups or so under the heading Soc.Genealogy.
Of course you can search all groups at once on the main page. Just be forewarned. In the search results, before clicking on something, take a look at what the title of the discussion-group is. This will likely give you a clue as to what posts you are likely to find in that group. This could change your mind on whether or not to read the post.