I finally compiled all the different Eagle parts I had drawn over the last year into a single Eagle library and adjusted them to be more or less uniform in look. While I was at it, I also added all missing chips and connectors. Currently, it contains the following parts:
Parallel Bus Interface
Parallel Bus Interface Device
Basically, it's everything you find on an 800XL motherboard.
Update 2014-04-29: added conversion to Eagle 6.5.0 (XML file format).