2+ iOS international keyboards

If you have two or more international keyboards configured, you can tap-hold the world globe key and then directly select one of the others. That's available in iOS 4.3.5, and may have been available in earlier versions. Tap by itself immediately takes you to the next keyboard.

I normally always have the Chinese (traditional) Handwriting keyboard configured. When I'm including bits of Chinese among English words, as opposed to writing longer text in Chinese, I normally use the English period instead of the Chinese period (。). The Chinese period takes up more space, presumably because within the Chinese context each character or punctuation mark should occupy the same amount of space as any other.

When I temporarily additionally configured the French keyboard, the order of keyboards was English-Chinese-French. I was mildly annoyed that I would have to tap twice to switch from Chinese to English, particularly because I'd be switching back and forth between the two languages frequently. Nice to learn that this is no longer an issue.
1/7/12: Even moreso since I recently added a fourth keyboard, Pinyin for simplified Chinese characters. I haven't devoted a great deal of time learning handwriting for simplified characters, so the Pinyin version of the keyboard for same is quite helpful.