Links related to Utilityradio:
Part 1 - Actual Frequency Listings

Nowadays there are not much actual books or databases on the market. Only a few still do exist, the others seems to have disappeared.

My recommendation would be still the 'Spezial Frequenzliste' from Funk Verlag Bernhard Hein, edited by Michael Marten. Not only because I have compiled several editions of this book in years before and traces of my work are still included but also because I know of the general attempt of the editor.
Still active is Joerg Klingenfuss. His books are dedicated to the RTTY section of the Utility world.
For NDB's there is an actual publication from Michael Oexner always fresh because published-on-demand.
For being up-to-date, you should note the 'Utility DXers Forum' organized by Ary Boender - it is well worth being there!
Another publisher, still active, is Roland Proesch, with books and lists

Part 2 - Audio Clips

Yes, there are a few pages with clips from utility stations on the web.

An excellent overview (and in-depth view) is from Leif Dehio on digital modes for shortwave. Unfortunately, Leif has a strange blocking policy.
Clips from ship/shore stations are on Sylvester Föcking's page, including the last words from the MS Titanic, which sunk in 1912.
Number stations are well covered by Simon Mason and Ary Boender, they are 'almost' real utility stations.
For broadcasting stations, you will find about every station on Dave Kernick's site.
a very interesting collection of clips from coastal stations is on the page of Andy Stumpf

The page of Nils Schiffhauer today holds many audioclips from the aeronautical bands on shortwave - an always interesting range to listen to !

Part 3 - QSL reproductions
A few utility QSLs can be seen on Ralf Kloth's site, as well as on Martin Elbe's site, together with broadcasting stations.
For broadcasting stations only, look at Manfred Hüppelshäuser's page, QSLs are paired with audio clips.
Interesting site: the QSL information pages of Martin Schöch, dealing mostly with BC QSLs
Many Utility QSLs are hosted on the page of Marcel Kurtz.
Or take a look at the site of Horst Ballenberger for some nice ones.
The Indonesian DX-Club features many QSLs, Utilities too, on their webpage.
another interesting page comes from Roland Bieri of Switzerland
Part 4 - Miscellaneous
From Italy, Andrea Borgnino has a fine website with lots of photos
The British website of Robert Maskill has very detailed information on coastal stations, from UK and worldwide.
See the page of Tom McKee for an interesting look on ship/shore communications of US inland waterways and great lakes.
Thomas Ingenpass has launched an exclusively German language forum on UTDX. Here you have many experts, and lots of discussions.
Another website with many pictures from antenna plants (a few are utility, yes) is up by Bernd Waniewski, an antenna technician.
On the page of 'Fenu' you will find lots of information on communication receivers, from ancient ones to actual SDR models
When you are interested in NDB-dxing, you should not miss the pages of the NDB List .
Heinz Schulz presents an interesting page, with many historical tables and pictures on Long- and Medium-Wave broadcast stations.
The site operated by Daniel Ekman has highly sophisticated info, many 'spy' stations are presented here...
Johan Veldhuis and Wim van Beek have collected many pictures of NDB installations
Nicole from the USA found an interesting item, a little away from our core interest - it's on car radio development
 ... more to follow ...