Don't know if anyone here frequents metafilter, but there was a good tip on it recently, pointing out that using a combination of
Google Book Search and
Amazon's Look Inside feature, you basically have McGee's ONFAC available to you in an electronic and searchable edition. Of course, you should probably buy the book too if you don't already own it, as it is amazing and indispensable, but
McGee himself advocates using electronic searching as a superior alternative to the index in the physical book.