Flower

Flowers are naturally occurring transparent blocks that are found in forest and plains biomes. Before 1.7, there were only two, dandelions and roses. After 1.7, the rose was removed and more flowers were added. All of the flowers can be used to make.

Dandelion
Common flowers, the only flower to have survived through 1.6 to 1.7. They can be crafted into one dandelion yellow. = 1 dandelion yellow

Poppy
Common flowers, and also the replacement of the rose. They can be crafted into one rose red. = 1 rose red

Blue Orchid
A light blue flower found in tiaga and spamp biomes. = 1 light blue dye

Allium
A rare flower. Alliums are only found in flower forest, and can be made into one magenta dye. = 1 magenta dye

Azure Bluet
A small, white flower found in plains and flower forests. = 1 Light Grey Dye

Tulips
Small flowers, found in 4 colors. Each type can be crafted into that color dye. = 1 (Red, orange, white, purple) dye

Oxeye Daisy
A white flower, used to craft light grey dye. Is found in plains and flower forest biomes. = 1 light grey dye

Sunflower
Sunflowers are two block high flowers. When fully grown, they will always face easy, giving you a good sense of direction. It can be used to create two dandelion yellows. Sunflowers are only found in sunflower plains. If right-clicked with bone meal, a sunflower will drop, but will keep the original sunflower in the ground. = 2 dandelion yellow

Lilac
Lilacs are two block high flowers. They are found in forests and flower forests. If right-clicked with bone meal, a lilac will drop, but will still keep the original plant. = 2 magenta dye

Rose Bush
Rose bushes are two block high flowers that are found in flower forests, birch forests and roofed forests. If right-clicked with a bone meal, a rose bush item will jump off the plant. = 2 rose red

Peony
Peonies are two block high pink flowers also called paeonia. It is found in forests, birch forests, flower forests and roofed forests. If right-clicked by a bone meal, a peony item will jump off the plant. = 2 pink dye

Cyan Flower
Cyan flowers replace roses (poppies) in the Pocket and Pi Editions. Cyan flowers are not going to be in the PC version. Since the 0.5.0 update, cyan flowers are named 'Rose' in the inventory. They cannot be turned into dye, and are only used for decoration.

Rose
Roses are only on the Xbox 360 Edition. They were removed from Minecraft PC in 1.7. They are crafted into two rose red dye. They are held and dropped by iron golems. = 2 rose red dye