Unlike prior versions, MT-Notifier version 3 does not have a full-fledged administration interface. It does, however, have two things that were not available in prior versions.
First, it makes full use of itemset actions, introduced with Movable Type version 3.2. Itemsets are simply lists of items - for our purposes, blogs, categories and entries. These itemsets have a drop-down list of actions that can be performed on the items in the list (the edit entry page also has a list of available actions, even though it is a single item, and not a "list" as such). When available, MT-Notifier will add items to this action list so that you may perform common tasks right from the Movable Type interface.
Second, MT-Notifier uses a new storage paradigm (a SQL table structure) that allows you to run queries on the data and manage it just like any other data in the system. This feature wasn't previously available, meaning you were dependent upon MT-Notifier for everything you wanted to do with your data. That is no longer the case. You can do this with any SQL-capable language or tool, or even the very powerful MTSQL plugin for Movable Type, right in a template, without having to use anything other than Movable Type!
More than one MTSQL template has already been posted, and as I find more, I'll add them to this list:
If you know of any other templates out there, let me know so that I can add them to the list.
Another user who goes by the handle of Blumunky has stepped it up a notch with his MT-Notifier Management Plugin, which doesn't require MTSQL at all, but adds a list of MT-Notifier subscribers to the list of Movable Type Notifications. Way to go, Blumunky! This was then updated for Movable Type 3.31 (and 3.32) by littlered. Sweet!