An international office supply company, known in full as Avery Dennison Worldwide Office Products. They're best-known for their labels, which come in a multitude of shapes and sizes. (Ok, so they're all rectangles -- but sizes vary from folder-label to full-sheet) In fact, Avery's labels are so much the standard that templates for their label sheets have been built into Microsoft Word. If your band's promo stickers (or for the truly lame, your tags) come out of the office printer when your boss is on break, they probably have Avery's triangle-A logo on the peel-off backside. They'll also disintegrate if rained on.
Avery was founded in 1935 by R. Stanton Avery in Los Angeles, but now operates out of Pasadena - possibly because R.S. first sold his sticky product under the name "Kum Klean". The Dennison bit was tacked on in a merger in 1990.