I want to put some breakaway headers into my Eagle CAD file. By that, I mean these:
Does Eagle come packaged with a library for these? If so, what is the part called, and which library is it in?
Eagle does indeed. The library you will want to look for is called
pinhead. It has various 2.54mm (0.1") pitch pinheaders in it.
If it's not on the list, go to the Eagle control panel window, right click on
Libraries and choose
Use all. Then, in the schematic window, go to
Library > Update all to update the libraries list.