Navel oranges (recognizable by the belly button-looking indentation underneath) don't have many seeds, making them great for salads or for snacking on. Valencia oranges are a good choice for juicing because they contain a lot of juice.  Blood oranges are rich-tasting and good for making marmalade, desserts, or sauces. If you want to make marmalade, try using half-blood oranges and half-Seville, so you can combine one of the sweetest oranges with one of the most tart.