In general you will not need more than your own letter of application and CV, the job specification/description and your own notes.
Your invitation to interview should detail everything you need to bring. Often employers request examination certificates, which can take time to locate, so make sure you check what you need in plenty of time.
You might wish to impress by reading up on the organisation's literature, e.g. a business plan or corporate social responsibility strategy, but make sure you have read it in depth and be prepared to share your views and ideas.
A pen and notebook are always worth carrying with you and, if giving a presentation, take a copy on a data stick even if you have emailed it beforehand, along with copies of the slides to use as handouts for the interview panel.
If you take a mobile phone, make sure it is switched to silent or off before entering the organisation.