I was recently looking for just this, as our school looks to transition from our old state standards in math and literacy to the common core standards. I thought to myself, someone has to have a question bank out there that is already mapped to each standard. Perhaps Examview format or an xml format would work.
Is there a way that educators could begin to work together to build such a bank, maybe through OER commons, curriki.org, some other common body. Now that the vast majority of the US has shifted to a common set of standards, there would be those to map questions/content to. There may be other international common sets of learning standards but I don't know much about that.
I have a hunch there is some paid content out there that could be added to your moodle (from ETS, examview, etc).
I have a hunch that one of the above open ed sites may have content available but it is hard for me to find. Partly, I don't know what to call it.