If you are not lazy - I recommend registering on spotify (this is done quite difficult) - there you can choose your favorite artists, and as soon as they release new songs / albums, you will receive notifications. Many also publish their own collections and playlists there. You will hardly find anything better.
Major online music publications usually post about releases first, such as resident advisor or mixmag. You can subscribe to labels and listen to a demo or full version on SoundCloud, for me, for example, it's most convenient there. You can also subscribe to youtube for your favorites, this is still a treasure trove of good.
Doesn't iTunes offer such a service? Alerter application.
Here's something else that was found on the Internet
album-info.ru service for monitoring changes in musical discographies.
ArtistShot 184.108.40.206 is an application, allowing you to follow new albums and concerts of your favorite artists
Well, there is something like album-info.ru the database is large, it comes regularly and on time. If your artist is on Youtube VEVO, why not subscribe there.