To celebrate de Bruijn's 90th birthday, TU/e organized a festive event. Quoting from the web site for that event:
A number of colleagues, friends and admirers of Dick de Bruijn, from all over the world, wrote a personal letter as a birthday present for his 90th birthday, on July 9, 2008. The collection of these letters can be downloaded here.
Dick de Bruijn's lecture at the day of the symposium has been recorded on film. This film can be seen via this link.
Addendum: One of the letters in the above-mentioned collection is from Donald Knuth. In the letter, Knuth says that de Brujin coined the word "multiset" in a letter addressed to him from 1968. Knuth's letter also mentions the work of three of my former colleagues and ICE-TCS members: Anders Claesson, Mark Dukes and Sergey Kitaev.