The Surveying.Org website plots a number of useful survey-related data features in a Google Maps interface; select one or multiple data features to display with a checkbox.
National Geodetic Survey Benchmark locations
Takes a few seconds for them to pop up. The different symbols correspond to various classes of accuracy for the benchmarks, both horizontal and vertical. Click on a benchmark icon …
… and get at popup with the name/designation of the benchmark. Clicking on the datasheet link brings up a full datasheet with coordinates, quality information, and more.
NGS Vertcon info
State Plane Coordinate System (SPCS) Zones
A few of the icons/popups are slightly misplotted, like the second one in the lower left, but they’re close enough to their respective SPCS zones to let you figure it out.
This is the only dataset that’s good for outside the US; UTM zones are displayed for the entire world.
Meridian locations for Public Land Survey System (PLSS) designations (Township/Range/Section)
Also slightly misplotted in a few cases, as with the Navajo Meridian above, but close enough to figure out.
Finally, you can put the web app into either line length or area mode, and then click on the map to define vertices for a measurement. Above, an area is defined …
… and the area given in various units. Click and drag on a vertex to move it; Ctrl-click on a vertex to delete it. Doesn’t seem to be a way to add a vertex to a line segment, though.