I have created the Celtic 
& Welsh Deities Master Post and other information relating to their practices throughout the site & forum. Some topics may contain other external links within the original post or throughout the replies.
This is not a complete comprehensive list of information. As more become available within the site & forum they will be added to the post!
Celtic
Aine
Aengus Og
Irish God of LoveBelenus
Brigid
- Brigid: Spells8 Lesson
- St. Brigid
Things You (Probably) Didn’t Know - More Stories of Brigid
- Tending Her Flame Of the Element Fire
- Invocation to the Goddess Brigid
- Brigid Doll
- Brigids Cross, 1st Attempt
- Pledges to Brigid
- Imbolc Ritual Ideas: Spells8
Danu
The Morrigan
- The Morrigan: Spells8 Lesson
- The Morrigan: Celtic Goddess
- Need some advice on Morrigan
- The Morrigan
- Any other followers of An Morrigan?
- Has anyone else learned about the Morrigan?
- A prayer or chant to Morrigan
- The Morrigan - Transformation Meditation
- Witch, Hekate, & Morrigan… Oh My!
- Two crows in front of me
- Meeting Macha - A little under 9 minutes
Tuatha De Danaan
Welsh
Arianrhod
Cerridwen
Rhiannon
Ogham
- Irish Tree Language - The Ogham
- Beith-Birch || Learning Ogham
- Fern - Alder || Learning Ogham
- Lus-Rowan || Learning Ogham
- Sail - Willow || Learning Ogham
- Ogham preoccupation…. I mean, project!
- Ogham? Runes? Witches Runes?
Other Related Information
- The Snakes
Of Saint Patrick - The Moon in Irish Folklore
- Sacred Irish Trees
- Dair/Oak - Magic in the Trees
- Tactical Magic in The Tain || Irish Mythology
- Transmigration of the Soul in Irish Folklore
- Ancient Irish Blessing
Samhain as an Irish Pagan- Lúnasa - A Brief History of the First Harvest
- When Deity Tells You No - My Bealtaine Experience
- Bean Sí
A Herald of Death - Celtic Fairies outside of Celtic Countries
Or close to it anyway.
I hope it helps you if you have anything your want to look into!