From 1998 on there has been a Domino Day world record attempt almost every year. Here you can find interesting information on the themes of all Domino Days:

Domino Day 2009: The World in Domino; The Show with the Flow
Domino Day 2008: Celebrating 10 years of Domino Day
Domino Day 2007: Falling into Life
Domino Day 2006: Music in Motion
Domino Day 2005: Domino Theatre of Eternal Stories
Domino Day 2004: The Challenge
Domino Day 2002: Expressions for Millions
Domino Day 2001: Bridging the World
Domino Day 2000: Action – Reaction
Domino Day 1999: Europa ohne Grenzen
Domino Day 1998: Visionland