Shadowfax:

The horse that Gandalf found in Rohan. Shadowfax was described to the Council of Elrond:
And there is one among them that might have been foaled in the morning of the world. The horses of the Nine cannot vie with him; tireless, swift as the flowing wind. Shadowfax they called him. By day his coat glistens like silver; and by night it is like a shade, and he passes unseen. (LOTR.280)

Shadowfax was the lord of the Mearas, those horses that only the lords of Rohan could ride, descended from the horse of Eorl. It is almost certain that he passed into the West with Gandalf and the Ringbearers in the year 3021 in the Shire Reckoning.

Shadowfax was given to Gandalf by Théoden, during the War of the Ring.

Stybba:

The pony given to Merry by Théoden. He is described as being grey and rather shaggy.

Strider:

The pony that Frodo rode back from Minas Tirith and rode on the journey to the Grey Havens.

Sharp-Ears:

One of the ponies belonging to Merry. Sharp-Ears was named such during the hobbits stay with Tom Bombadil. When the Prancing Pony Inn was raided, the ponies fled to Bombadil, who later sent them to Butterbur.

Swish-Tail:

One of the ponies belonging to Merry. Swish-Tail was named such during the hobbits stay with Tom Bombadil. When the Prancing Pony Inn was raided, the ponies fled to Bombadil, who later sent them to Butterbur.

Simbelmynë:

These were the flowers that grew on the Rohirrim barrow-graves. The translation from the Rohirrim tongue is "evermind".
Upon their western sides the grass was white as with a drifted snow: small flowers sprang there like countless stars amid the turf. (LOTR.529)

The flowers were special in that they bloomed in all four seasons, winter, spring, summer and fall:
Evermind they are called, simbelmynë in this land of Men, for they blossom in all the seasons of the year, and grow where dead men rest. (LOTR.529)

The Second Age of the Sun:

In the beginning of this Age, Númenor was raised as a reward for the Edain that had fought on the side of the Valar. Near the end of the Age, Númenor was destroyed and the end of the Age was the end of the War of the Last Alliance.

Other events of the Second Age include:

The building of Barad-Dûr in Mordor
The creation of the Rings of Power and the One Ring
The appearance of the Ringwraiths or Nazgul
The founding of Gondor and Arnor after the destruction of Númenor

The Lord of the Rings
The Silmarillion
The Unfinished Tales
The Hobbit
The Complete Guide to Middle Earth by Robert Foster