Suet is one of the most popular bird foods. It's the best food to attract woodpeckers, and among the other birds fond of suet are wrens, chickadees, nuthatches, kinglets, thrashers, creepers, cardinals, and starings. Mixtures of suet and peanut butter may attract woodpeckers, goldfinches, juncos, cardinals, thrushes, jays, kinglets, bluebirds, wrens, and starlings.
Some birds don't eat seed or suet, like hummingbirds and orioles. You can attract these birds by offering sweet nectar for them to drink. You can buy a special nectar mix, or you can make it yourself by combining one part table sugar to five parts water. Store the unused mixture in the fridge and watch the birds flock to your feeders. Just make sure that you don't leave the mixture more than a few days, especially if it's hot outside - the nectar will ferment.