Some popular edible flowers

Borage - produces star-shaped, sapphire-blue flowers with a fresh, cucumber taste, perfect for adding to salads and summery drinks but just as happy crystallised or sprinkled on to sweet things. It is a hardy annual. Sow under cover in early spring and plant out in early summer in a sunny spot with well-drained soil. After the first year, borage should self-sow freely.

Calendula - is a well know edible flower easy to grow, with bright yellow-orange flowers. They are fast growing and have many culinary uses, including salads, garnishes, cakes, desserts, savoury cooking, food colouring, hot & cold drinks.

Cornflowers - are easy to grow annuals which flower during the summer. They are generally blue in colour. They look fantastic in borders, particularly when planted in drifts, and provide a rich source of nectar for bees and butterflies. Cornflowers add vibrant colour to salads, sweet and savoury dishes.

Dianthus - are popular edible flowers which make lovely additions to salads, and are ideal for sugaring to add to cakes and desserts for unusual and colourful decorations. A compact plant which grows up to 15cm tall; they are perfect for containers and small gardens.

Fennel -The mild anise/liquorice flavour combines well with fish, meat and vegetable dishes.

Lilac - Mix fresh fragrant flowers with a little cream cheese and serve on crackers or stir flowers into yogurt to add a hint of lemon. Also useful as a garnish for cakes, scones or sweets.

Marigold - have a peppery taste and look beautiful sprinkled over food. This is a hardy annual – sow where it is to flower, in early to mid-spring. You will get quicker growth and stronger, earlier-flowering plants if you start them off under cover and plant outdoors once the weather has started to warm. You can use flowers straight away as a garnish on soups and salads or you can grind with a little olive oil to create a "poor man's saffron" for colouring dishes.

Nasturtiums - are a fast growing annual and incredibly easy to grow. They come in a wide variety of colours and types, with some being suited to containers, whilst others are useful for covering walls or trellis, providing ground cover or trailing from hanging baskets. Nasturtiums have a strong, peppery taste, are an easy to use and versatile edible flower with edible leaves, flowers, stems and seeds.

Rose - the petals have a delicate flavour which will improve cool drinks and fruit dishes, or why not try rose petal jam? Rosehips and petals can both be used in jellies. If the flowers are crystallised, they will make attractive cake decorations. It is best to remove the white heel from the base of the petals before eating.

Viola - (tri colour) looks like a miniature pansy with five petals which are generally purple with some white and yellow. Viola is an easy to grow, hardy annual and are a popular edible flower, with a wide range of uses. They are most commonly used to decorate cakes and desserts, are ideal for sugaring and beautiful when scattered over salads or used as a garnish.

You can find more information about edible plants at:
Garden Organic
RHS (Royal Horticultural Society) 
Thompson and Morgan

There is also a large variety of books about edible flowers such as:

The Edible Flower Garden by Kathy Brown

Edible flowers by Kathy Brown

The Edible Flower Garden by Rosalind Creasy

Cooking with Edible Flowers by Miriam Jacobs