Ultimately is a way of imposing a certain type of order on the world. As we collect things, we engage in a process of mental ordering—categorizing objects, ideas, memories, etc. Collections are great resources for inspiration and creativity.
One wonderful collector that I have met is J.P. Williams, He is a graphic designer in New York and was a student of Paul Rand. I met him on a design field trip in 2009. He is known for saying, "You are only as good as your obscure resources." He lives this principle through collecting. He collects neat things, such as the security patterns on the inside of envelopes, as well as various types of string from all around the world. His work is wonderful and it is surely inspired by his collections.
I like collecting images on Pinterest. I often post images that I have found on the internet, but the most helpful resources have often been images that I have found outside the internet—images from books that I have scanned for example.