B.R.I.D.G.E TO DATA (BTD) is the prevailing resource for capturing detailed global metadata on real-world databases.  The developers of BTD have spent meticulous thought into creating a process for collecting (and maintaining) data by building relationships with key data vendors across the world.  With the breadth and magnitude of global real-world data available, it’s a testament to the scientific staff at BTD to successfully achieve such an ambitious undertaking.

It is impressive that your list is getting longer. The search engine (B.R.I.D.G.E. TO DATA) is useful when a researcher gets overview of various databases at a glance.

This "database" of databases is very useful in my day-to-day activities as it allows me to find quickly which databases will fit the best regarding the research questions I have. It is very complete and contains information on countries for which it is sometimes difficult to find information elsewhere.