One database that I've been investigating recently is Massachusetts, Town Clerk, Vital and Town Records, 1627-2001. This database has vital records for many cities in Massachusetts, and I specifically found a few of my ancestors' birth, death, and marriage certificates for Boston.
Unfortunately, the records in this databases are not indexed, so finding specific records takes a bit of know-how and time. I'll do a step-by-step tutorial of how I found the death record for my 3x-great-grandmother Margaret Dailey Fitzgerald.
We're going to go to the main Massachusetts, Town Clerk, Vital and Town Records, 1627-2001 database from categories U.S. > Massachusetts.
Here, we're looking for Boston, which is Suffolk County.
Within Suffolk County, we're going to select Boston.
Margaret Fitzgerald died on 14 April 1889, so to find the record number, we're going to go the death index, and select the database for 1882-1891, and because her last name began with "F", we'll select A-H.
We'll now search the index , which is listed alphabetically by the deceased's last name. Listed under "Fitzgerald", I found a listing for a Margaret who died in 1889 at the age of 80 (it's a little hard to read). This is probably her, so I'm going to note the corresponding record number, which is 2867
Now we'll get out of the death index search, and scroll down to deaths... the record number we're looking for is 2867, so we'll go into the database where that number will be.
The record numbers are usually (not always!) in chronological order, so after a bit of flipping through, we find her actual death record!
If you have a vital record in the form of a register list, the record numbers will probably be located next to the entries for each person. In this fortunate case, you can save time looking up the record number!
Hopefully, new records will be added to this database. I wanted to get death records for my 2nd great-grandfathers Thomas Fitzgerald and Thomas Ryan, who both died in 1916. The death index includes 1916, but the actual death records only go up to 1910-- you can get record numbers, but, annoyingly, not the records themselves.
Don't forget to explore these Massachusetts town records!