Hi! I collage as part of prep work for my paintings. While I do receive junk mail that works for my purposes, I don't receive enough diverse subject matter to make very interesting compositions. That is, I didn't, before I subscribed to every free catalogue under the sun. I found that most of the links on the following website remain active, https://dealtrunk.com/free-catalogs/, but with every passing year, more stores are moving away from print catalogues.
Fashion magazines are ideal. Now they're a bit more difficult to get ahold of for free, but if their subject matter corresponds to your career field, you can request a free temporary submission. The following website, https://www.freeflys.com/save-money/free-magazines-in-the-mail/, links to forms to fill out if you'd like to fill out a request.
My county has a free magazine for advertising local events and businesses. They release this maybe twice a year. I always grab a copy when I stop at the grocery store, thought they're available at many of the small businesses listed within its pages, which is to say, those that are customer facing, such as small stores and the like.
I'm also part of my local Buy Nothing facebook group. Sometimes folks will be clearing out space and want to unload years worth of magazines. That's like Christmas for me. My local library likewise has a free section for super outdated magazines and I grab the ones with large color photo spreads or illustrations.
You can get lucky in the waiting areas at airports and other in-between points in public transport. Sometimes folks will buy a magazine and then leave it behind when they board their flight or train. Maybe even intentionally. Who knows? But their loss has been my gain in the past.
Whether you collage or you're genuinely interested in the content, I hope these tips prove useful for you! Thanks for stopping by! I put out a new blog post every Monday. Toodles!