In a recent webcast, IBM demonstrated several aspects of the search capabilities in IBM Mail Next.
Once of these was 'faceted search', which allows users to choose elements of the result set (facets) and refine their query using that data.
To show how our search product, the FT Search Manager, can also provide faceted searching, we've put together the short video below (the other Mail Next search functionality mentioned, searching Sametime Chats Transcripts, we can already do).
Please note that in our product you can construct search results using any combinations of fields, text and @formulas. In all cases, the tool will correctly identify the type of result data (text, mail address, date, number etc), and allow you to select facets based on that. For example, an Email address will let you choose the sender or domain, a Date will let you choose various timeframes around the selected date, a Number will let you add margins to the selected number etc. And this works for any application you search, not just Mail.
To try this yourself, please download the no-obligation, no-install demo from http://www.ionetsoftware.com/search, and start searching.
FTSM V6 Faceted Search Demo