http://www.tilt.it Federico Croci's web site.
http://www.zaccaria-pinball.hu Petrik László's web site.
http://www.pinrepair.com Clay's web site. No Zaccaria specific information here, but lots of advice and information on pinball machine repair and restoration.
http://www.pinwiki.com/Much general information. Includes an archive of Leon's web site.
The rec.games.pinball usenet newsgroup.
Federico Croci started a Zaccaria-specific mailing list hosted on Yahoo. Go to http://groups.yahoo.com/group/zaccaria/ and sign up.
Zaccaria video games are covered at http://www.zzzaccaria.com/.
2650A processors are available from Chris Koekoek in the Netherlands.
2650A processors have recently become available via Mark Capps. Visit his web site at http://www.arcadechips.com for details. He also has 2101 and 5101 RAM chips, 6821 PIAs, SN76477 sound chips, TMS5200 and TMS5220 speech synthesizers, and 6802 processors.
Aeneas Verhe's site http://www.flippers.be has some coverage of Zaccaria and other European pinball manufacturer's games.