Which analytic stats are actually useful and should be looked at?

https://www.naturalstattrick.com/# is good because a) it provides most of the well known analytics and b) it's not behind a paywall

[url]https://hockeyviz.com/[/url] has some nice visuals but it's partially behind a paywall. It gives a snapshot of a player, team, game, etc.

For more sortable/in-depth things the site mentioned above is the one I go to.

evolving-hockey.com

hockeyviz.com

naturalstattrick.com

moneypuck.com

All four are excellent resources for all different things. The first two have some things behind a subscription paywall, but in my opinion they're both well worth it.

Also check out Corey Sznajder's manual tracking project (https://public.tableau.com/profile/corey.sznajder#!/), which is another awesome resource for things not available in public NHL data, namely transition data.