There was an old much-referenced page about octane boosters, originally found at: http://www.idavette.net/hib/fuel/index.htm

Unfortunately, the link is dead. Fortunately, web archive has it:
https://web.archive.org/web/20090227052008/http://www.idavette.net/hib/fuel/index.htm
https://web.archive.org/web/20090227052058/http://idavette.net:80/hib/fuel/page2.htm

In case that doesn't work, data copied here for posterity after the jump.