AGE UK has an excellent and well structured website with information on everything you need to know about benefits. The website includes a benefits calculator - a simple online tool where you can find out if there are any benefits you might be able to claim for.
Whilst some of the information relates to older people, much of it applies to any age group.
As well as having information on different benefits and allowances, the AGE UK website has information around everything you need to know to make sure you are not missing out. Each of the links below will take you to the relevant section of their website.