The current ways to keep track of collections are:

• Writing them down (as a local .txt or in the description of your MB profile or collection) which are not fun to maintain
• Bookmarking them, which unless you have synced bookmarks means they can't be accessed on multiple devices

It would be cool if collection collections were an option, for example a favorite collections, collections with a fun theme or interesting owned releases collections.
On Rate Your Music this is possible by copying the list code into a new item (although this connection doesn't seem to appear on the original list's page)
The columns could be something like:

 One thing to keep in mind is that private collections could be included in public collections (if they're a collaborator so they know the link or a collection went private after adding it), the information about that collection should not be displayed to anyone who doesn't have permission to view it.