http://www.tilt.it Federico Croci's web site.
http://www.flipper-pinball-fan.be Leon's web site.
http://www.zaccaria-pinball.hu Petrik László's web site.
http://www.marvin3m.com/fix.htm Clay's web site. No Zaccaria specific information here, but lots of advice and information on pinball machine repair and restoration.
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.
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.
Frank Gigliotti has been working on backglass artwork reproductions on plastic films. If you have a game without a backglass, he may be able to help you. You can see samples at http://mysite.verizon.net/frankgigliotti/index.html, or reach him at luvthathatapex at verizon dot net.
Aeneas Verhe's site http://www.flippers.be has some coverage of Zaccaria and other European pinball manufacturer's games.