When I was bottling, I used 3/4" round Avery labels and stuck them on the caps. Not as spiffy as full labels on the bottle, but nicer than marking the caps with a Sharpie, and a lot easier to deal with than regular labels. They come off with the cap, so there is no scraping or cleaning them off. There is an Avery MS-Word template available online - just search for the label's product number.