Chess24 has an improving playing zone and worthwhile news reports, but their biggest attraction is their growing library of video series. The most noteworthy series was by Peter Svidler on the Gruenfeld, but there have been many other interesting ones as well. Still, when a player of Svidler's caliber engages in such a project it's likely to be something special, and that was certainly true of the one on the Gruenfeld.
Now Svidler has released another opening series, this one offering a White repertoire in the Ruy Lopez with the very trendy 6.d3 (after 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.0-0 Be7). Nowadays this is considered a more promising way for White to avoid the Marshall Gambit (6.Re1 b5 7.Bb3 0-0 8.c3 d5) than the standard 8th move dodges like 8.a4 and 8.h3, and it has almost become the new main line of the Ruy. Svidler acknowledges that it doesn't seem to promise White an advantage - what does? - but aims to offer White fresh ideas that will at least put the onus on Black (especially if he hasn't already prepared for those them) to solve new problems.
Svidler has long been a specialist in the Ruy, having played both sides of the opening with great regularity for the past 20 years or so; indeed, he states that he probably knows this opening better than anything else in his repertoire apart from the Gruenfeld. So the series should be a very attractive one to anyone who plays either side of the opening, and also for those who simply want to understand the game better; the Ruy is an extremely rich opening.
As usual, there are two ways to access the series. One is to buy a premium membership on the site for $135.99 for a year (pricy, but if you like watching chess videos it's a good deal), and the other is to buy the series a la carte for $14.99 - not a bad deal at all. (It would be an even better deal if Chess24 would finally create the downloadable PGN files they've promised since the site's inception, but even without that it's a very good price in comparison to comparable video series across the landscape.)
UPDATE: As noted in the comments section, there's a third way to access the series, which works for all the other series as well: purchase a one-month membership for $13.99.