Eagle: How do I make a component from a board?
I've used 2 different methods for scavenging components out of Eagle projects.

Automated method.  Run exp-project-lbr.ulp, then sort through the automatically generated library.

Manual method.  Originally from here.


Select the parts you want to copy with the group select tool. 
Use the scissors button on the toolbar.
Right-click the group or hit the GO button after clicking the cut button. Eagle wants to know what it is you wish to "cut", which is really more like the "copy" command in most apps.
Open the new file and do a paste, it should copy the info.