i2Bopomo - Free Online BoPoMoFo (Zhuyin) Input Method

Bopomofo, Zhuyin, or Mandarin Phonetic Symbols, is an online Chinese transliteration keyboard for Taiwanese Mandarin. Bopomofo consists of 37 characters and 4 tone marks that transcribes all possible sounds in Mandarin. The word Bopomofo (ㄅㄆㄇㄈ) is derived from the first 4 syllables in the conventional ordering of available syllables in Mandarin Chinese. Zhuyin is the most commonly used phonetic system in Taiwan elementary schools to teach students reading and writing.