You can reduce the amount of catalogs and direct mail that you get in the mail (in the U.S.) by registering with dmachoice.org and catalogchoice.org. I opted out of insurance of and credit card offers. The next time I get a catalog, I'm going to use the site to get off the list.
Why do this?
Well, catalogs are wasteful. If you're reading this, you're "wired". Chances are you buy, sell, and trade online, with ebay or craigslist, or from an e-retailer. Snail mail belongs to another century.
Paper is wasteful, especially if it just goes into the recycle bin. Minimalism isn't just minimizing one's financial footprint, it's your eco footprint as well. In other words, don't kill trees for no reason. Kill bits instead :-)