Most useful NON-COMBAT skills?

[OyajiBR☕]

I started recently, so far I noticed that the spells speak to the dead and speak to animals are quite useful. I'll save all scrolls and potions I get. Lockpicking items are obvious to mention, but just to remember... Anything else?

[cfehunter]

You can get an amulet to speak with the dead right at the start of the game, so it's not worth taking as a spell for yourself.
Speak with animals is *incredibly* useful.

Flight and misty step are also very useful out of combat. Besides that there's everything that helps you make dice checks, friends is probably the most powerful.

[His Divine Shadow]

Misty step, speak to the dead, speak to animals, remove curse, and knock. So scrolls or spells. Also, detect thoughts

[Clive Hawkins]

Find Familiar
Longstrider
Enhance Leap
Featherfall
Diguise Self
Silence
Detect Thoughts

All of these are "Ritual Spells" that do not use a spell slot when casting them outside of battle. They make map traversal a breeze and give you decent dialogue choices if you aren't a character with high Charisma.

[dustin1280]

The following spells are all rituals which means can be casted for free (no spell slot usage) outside of battle:

Detect Thoughts: Character can focus their thoughts to read the minds of specific creatures. Last until your next Long Rest.

Disguise Self: Disguise the character as any other race or gender. Lasts until character is fully rested.

Enhance Leap:
Triples a character's jumping distance. Lasts for 10 turns.

Feather Fall: Character and the party gain Immunity to Fall Damage. Lasts for 10 turns.

Find Familiar: Character summons a Familiar, a Fey spirit that will take the form of an animal of the player's choosing. Lasts until they are dismissed, and a Short Rest is needed to resummon.

Longstrider: When a character touches a creature, movement speed will be increased by three meters. Lasts until the next Long Rest.

Silence: Creates a sound-proof dome which will Silence everyone inside, while making them Immune to Thunder. Targets can also become Hostile.

Speak with Dead: Brings a corpse back to life to answer five questions. Lasts until the next Long Rest.

Other useful utility spells that cost a spell slot are Misty Step and Knock

[HappyThoughts]

Longstrider is very handy. It's a ritual spell so it doesn't cost a slot if cast outside of combat and it lasts until your next long rest. +3m for your whole team is just really handy.

[LoganTheDragon]

Skills:
Persuasion/Deception/Intimidation are useful for dialogue interactions, as is Insight which tells you when people are lying.
Perception is good for spotting ambushes/traps/buttons/levers.
Survival is good for spotting dig sites (where you can dig up chests), as well as spotting vines and other "nature" that might harm/impede you.
Arcana/Religion helps you get more information about magical or religious artifacts or locations you may come across.
Acrobatics helps keep you from falling prone when you jump farther than you can safely land, Athletics can help keep you from taking as much damage in these situations as well.
The most helpful of these are probably (imo): Persuasion, Perception, and Survival.

Spells: the ones others have mentioned, imo the most helpful have been
Featherfall and Enhanced Leap, both of which do not cost a spell slot when cast outside of combat because they are "ritual" spells. They make traversing the environs much easier (or in some cases possible instead of impossible).