I ordered a CD from an online music store. My confirmation email reads "your order has shipped." English is not my first language, and this strikes me as odd. Shouldn't it be a passive-voice sentence, i.e. "your order has been shipped"?
I don't know why someone downvoted, 39 - I'm having quite a job finding corroboration in online dictionaries for the following.
Some verbs in English have a dual usage, where a transitive usage may be switched to an intransitive one, the direct object becoming the subject:
Such a usage is called the ergative usage.
I'd distinguish this from the middle voice, a similar construction where a property of state rather than an action is being described:
I'm sure that the verb ship can be used ergatively, but it doesn't appear in Wikipedia's lengthy list, and the following is the only support I've found for my analysis:
ship: To go aboard a ship ... (AHDEL)
(obviously, to ship = to send by ship is a well-known transitive usage)
I'd add that the meaning of 'ship' (transitive) has been broadened to 'send by, or as if by, ship', and so that of 'ship' (intransitive) has followed, being broadened to 'be sent off'.