The Mnemosyne Project

This is the standard phonetic alphabet used when you need to unambiguously communicate letters over radio or telephone. Officially used by militaries, aviation, shipping, etc.

Alfa, Bravo, Charlie, Delta, etc.

This deck includes only one-way cards (e.g., "Question: Z, Answer: Zulu"), on the assumption that you don't need much practice to go the other way.