Some hosts offer similar (but not same) tools but from the sounds of it you are basically running a content management system where presumably nominated users are allowed to submit content which is vetted prior to publishing ?
If that's the case then any one of a number of Open Source Content Management Systems could potentially be used.
Getting your current data out in a usable format could be an issue, but once you have it you can inject it into anything with the right jiggery pokery.
Take a look at Wordpress (with one of the excellent CMS plugins to convert it from blogging engine to CMS) Joomla, CMSMadeSimple and MODx. Between them they cover most needs.
Most hosts offer one-click installs of the more common CMS scripts, which simplifies installation but does not address how to port your current content across to a different platform.
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