Some feats and class features let characters cast ritual spells, and as far as I can tell there is no list of them in the Player’s Handbook. Here’s a collection of them so you don’t have to go through the spell list entry by entry.

Rituals-By Level
1st Level
Alarm
Comprehend Languages
Detect Magic
Detect Poison and Disease
Find Familiar
Identify

Purify Food and Drink
Speak With Animals
Tenser’s Floating Disk
Unseen Servant 

2nd Level
Animal Messenger
Augury
Beast Sense
Gentle Repose
Locate Animals or Plants
Magic Mouth
Silence

3rd Level
Feign Death
Leomund’s Tiny Hut
Meld Into Stone
Phantom Steed
Water Breathing
Water Walk

4th Level
Divination

5th Level
Commune
Commune With Nature
Contact Other Plane
Rary’s Telepathic Bond

6th Level
Drawmij’s Instant Summons
Forbiddance


Rituals-Alphabetical
Alarm (1st)
Animal Messenger (2nd)
Augury (2nd)
Beast Sense (2nd)
Commune (5th)
Commune With Nature (5th)
Comprehend Languages (1st)
Contact Other Plane (5th)
Detect Magic (1st)
Detect Poison and Disease (1st)
Divination (4th)
Drawmij’s Instant Summons (6th)
Feign Death (3rd)
Find Familiar (1st)
Forbiddance (6th)
Gentle Repose (2nd)
Identify (1st)
Leomund’s Tiny Hut (3rd)
Locate Animals or Plants (2nd)
Magic Mouth (2nd)
Meld Into Stone (3rd)
Phantom Steed (3rd)
Purify Food and Drink (1st)
Rary’s Telepathic Bond (5th)
Silence (2nd)
Speak With Animals (1st)
Tenser’s Floating Disk (1st)
Unseen Servant (1st)
Water Breathing (3rd)
Water Walk (3rd)