Suet feeders attract some of my favorite birds, like nuthatches and woodpeckers. For years, I've bought suet cakes each winter. This year, for the first time, I tried making my own, a project that was surprisingly easy and successful.
The idea came when I was separating the fat from a pot of chicken stock. I was making soup from the broth but the fat was going to be wasted. I'd just refilled my suet feeders so I had an an empty tray from a commercial suet cake. I put a handful of bird seed (a mix of cracked corn and black sunflower seeds) into the tray and then poured in the melted fat. Stir a couple of times, then out on the porch to harden.
The first homemade cake was a little thinner than the commercial ones, but it worked in the feeder and the birds liked it. The next batch, I had more fat so I made them thicker. My homemade suet was relatively soft and I think it would melt in hot weather, while the factory ones have stabilizers. For me, that's not an issue since I only use suet in the winter.
Suet cakes are cheap enough that I wouldn't recommend buying ingredients just to make homemade suet, but if you have birdseed & fat already, it only takes a few seconds to make them.
I teach economics at Kalamazoo College. My wife is also an economist. We were on sabbatical in Europe for the 2014-15 academic year. (Salamanca, Spain, followed by Oxford, UK.) We were in Uruguay for the 2006-7 academic year.