The current draft of C++0x requires that a moved-from object can be destroyed or assigned to. If you pass your object to a function in the standard library then that is all that is assumed.
It is generally considered good practice to ensure that a moved-from object is a "working" object of its type that satisfies all invariants. However, it is in an unspecified state --- if it is a container, you don't know how many elements it has, or what they are, but you should be able to call size() and empty(), and query it.
The current draft is unclear on what is required of the standard library types themselves, and there is active discussion in the C++ committee about that.
