The Feast of Great-Winter, also called the Feast of Winter Veil, is an in-game, end-of-year, week-long holiday event roughly corresponding to Christmas.
Info from the official site
The Feast of Winter Veil is upon us, and Greatfather Winter is busy spreading holiday cheer in major cites across the land! Here are a few holiday treats players can now experience in-game:'Twas the feast of Great-Winter
And all through the land
All the races were running
With snowballs in hand.
The cooks were all frantic
And for those "in the know"
Swoops and owls were crashing
Like new-fallen snow.
Cookies and eggnog
Were consumed by all
As the snowballs flew freely
And drunks smashed into walls.
May your feast of Great-Winter
Be one merry and bright
And from all here at Blizzard
We wish you a fun night!
- The Jinglepocket Goblins have set up their seasonal fare shops in major cities. Adventurers can purchase many holiday favorites - including Greatfather's Winter ale, candy canes, gingerbread cookie recipes, and mistletoe.
- All the cheer-spreading is making Greatfather Winter hungry, and he is looking for adventurers to get him his daily fix of milk and cookies.
- Smokeywood Pastures needs a few brave adventurers to investigate the disappearance of a shipment of holiday goods traveling though Alterac.
- Unconfirmed reports say that consuming eggnog during a snowball fight can have some chilling results.
- January 2nd is the last day of the Feast of Winter Veil.
- Kissing a 'Winter Reveler' under mistletoe will magically create for you 5 sprigs of Mistletoe ... You can also get Fresh Holly  (x5), which can be used to transform your mount into a reindeer for thirty minutes...
- There are snow mounds, Holiday Snow (τ), in the snowy parts of the Alterac Mountains during this event. You can pick up Snowballs (τ) off them. They have a knock back effect so use them wisely.
- There are special snow mounds, Hardpacked Snowdrift (τ), in Alterac Valley during this event. You can pick 5 Hardpacked Snowballs (τ) off them. They have a knock back effect so use them wisely.
- Around this event, Blizzard forum posters use this portrait: <imagelink>http://forums.worldofwarcraft.com/images/portraits/bliz/xmas.gif%7Cexternal</imagelink>
There are several special items and plans that are only available during the Feast of Winter Veil.
- Greatfather's Winter Ale 
- Candy Cane  - Restores 61 health over 18 secs
- Holiday Spices  - Used to make Gingerbread Cookies and Egg Nog.
- Holiday Spirits  - Used to make Egg Nog.
- Snowball  - Throw them around!
- Recipe: Gingerbread Cookie  - Cookie that restores 61 health over 18 secs, also gain Well Fed (+2 stam & spirit) for 15 mins
- Recipe: Egg Nog  - Drink that restores 61 health over 18 secs, also gain Well Fed (+2 stam & spirit) for 15 mins. If you're hit with a snowball while under the influence of Egg Nog, you turn into a snowman!
- Schematic: Snowmaster 9000  - Makes 1 snowball per day.
- Formula: Enchant Weapon - Winter's Might  - +7 damage with frost spells
- Plans: Edge of Winter  - Blacksmithed 1H Axe
- Pattern: Gloves of the Greatfather  - Leather gloves
- Recipe: Elixir of Frost Power  - +15 frost damage for 30
- Pattern: Green Holiday Shirt  - Green Shirt
- Winter Veil Disguise Kit 
- Wand of Holiday Cheer 
- Graccu's Mince Meat Fruitcake