I usually look around at local Craigslist, garage sales, thrift stores, curbside on garbage nights (you'd be surprised what kind of furniture they're getting rid of) or at my place of employment of any shelving units they're tossing away in the trash for possible shelving ideas.

I grabbed one on one of my courier route stop last year and currently awaiting the boss's decision on one unit if she doesn't have a use for it in the media library anymore.

I also have a metal shelving unit I grabbed from work several years ago I had forgotten about.

I try to find any useful shelving unit ideas for free.