Has anyone ever seen a plugin for MovableType that will allow a blog owner to moderate entries? e.g., I could give people access to compose blog entries, but only I could make them go live? The sort of thing you might use in a shared-blog type of situation where someone wants to be sanity-checking the things that people are making live to the world?
Alternatively, are there any decent pieces of blogging software that handle this nicely with similar feature sets to MT?
wordpress can. see http://codex.wordpress.org/Roles_and_Capabilities
Just tell your contributors to save as a draft and let you publish.
I go even further and just ask for contributions by e-mail, since I run everything through BBEdit for spelling and grammar checking, HTML link verification, smart quote and gremlin filtering, etc.