If you'd like to learn the Navy signal flags, you can download some flash cards from this page. The flash cards are in a Word file designed to be printed on cardboard or on perforated business card stock.
The file is a self-extracting ZIP file that contains separate documents for the fronts of the flash cards, the backs, and some brief instructions. All you need to do is download it and double click it.
For those whose Internet providers don't allow .exe files to be downloaded, here's a version in non-self-extracting ZIP format: