Well, for the genealogist and historical researcher, they're all great places to look for historical sources and information on ancestors, historical figures, or the local area. And they've recently been incorporated into my Historical U.S. County Boundary Maps tool! Just check the "Show Research Locations" checkbox and then select which categories you want to show, and symbols will appear on the map:
Then, you can click an icon, and an info window will appear:
The name of the place and the Website are both hyperlinks, which will open up a Google Places page for more information on the place:
I've thought about having the cemetery info windows display links directly to that cemetery's findagrave listing (or a similar site). Let me know in comments your ideas on what site(s) I should have the places link to.
By the way, when you choose "courthouses", you'll also see city halls; when you choose "churches", you'll also see synagogues, mosques, hindu temples, and other places of worship.
TIP: The closer you zoom in, the more places you'll see. This is because the map limits the number of places displayed to 20 to help cut down on clutter. So when you're zoomed out too far only 20 places will appear, and many places will simply not appear until you zoom in closer to the area you want to explore.