Two options for marking your items
If you're an artist, woodworker, or just someone who likes to identify things as yours, here are two options.
Both are suggested by Chris Schwarz, a woodworker who (FWIW) tries to buy from small, independent companies that treat their workers decently. So presumably these companies do the same.
The more economical option is a custom rubber stamp. See his blog entry here. You can submit a logo, drawing, or what-have-you, and they'll make you a rubber stamp.
An alternative is to get a custom metal punch -- with your name, logo, or whatever. See here. This option is more expensive -- the woodworking punch is US$160 -- but presumably it lasts a lifetime. They also have punches optimized for leatherwork, plastic, and others.