Detect Thoughts (Wizard)
Disguise Self (Cleric, Wizard)
Enhanced Leap (Druid, Wizard)
Feather Fall (Wizard)
Find Familiar (Wizard)
Longstrider (Druid, Wizard)
Silence (Cleric)
Speak with Animals (Druid)
Speak with Dead (Cleric)
I play a wizard and can cast any ritual spell I know out of combat without using up a spell cast slot. Even though the spell will list the cost as spell slot 1 or 2, it will cast without using the slot.
Out of combat, you just have to add the ritual spell to prepared spells, cast it then remove it and add another type of spell.
Other classes can add ritual spells as a perk at level 4.
(I made level 4 last night and looked into it when I saw the Ritual Spells perk. Wizards will not need to take this perk. They only need to learn/have ritual spells in their spell books.)