Teemu Leinonen posted a link on the IIEP-OER list, referencing the LeMill project he's working on. I just checked it out, and it's pretty cool. This one is based on the Plone content management system / framework, so it's great to see what can be done on top of these maturing platforms.
It's still being developed, but it looks like LeMill is another great option as a CAREO replacement. It's got some things in it that CAREO lacks (collections - an evolution of "subscribed objects", tagging), but doesn't have comments/discussion for each item (yet?). It's multilingual, easy to install, and runs just about anywhere.
Repository really isn't the right term any more. LeMill is (intended to be) more of a community than a repository. That's a much better model - one that seems to be working well on other projects like SocialLearning.ca (and many others - perhaps Merlot is the granddaddy of them all?)
I like the distinction between "pieces" (assets - images, video, etc...) and "materials" (compound products - websites, learning objects, courses...). The resource addition (upload or reference) process was pretty simple - maybe too simple, since there doesn't appear to be a license selector or copyright description available. I had an image uploaded and tagged in about a minute, though.
update: found a page on the LeMill wiki describing mandatory IEEE LOM metadata fields, so perhaps that widget just isn't exposed for Pieces...
Where LeMill stands apart is the concept of Activities and Tools - perhaps these are just variations on a theme, and might be analogous to the different content types they've got in SocialLearning.ca. The implementation of the different content types lets you do some interesting things to group/sort/categorize/display various items, so that's a handy step in the right direction.
I'm going to have to make some time to play more with LeMill, and to finally get around to mocking up a Drupal port of CAREO.