It's not often that I see a great new ideas for freezing food, but this is definitely one for the books, uh, blog.
Take a pound or two of raw hamburger meat, put it in a freezer bag and flatten and measure off portions with a chopstick!! When you want to use some (like make just one fresh hamburger just open the bag and break off however much you want to use. This is a really practical idea. I still love my gravel also though.