BBC Bitesize covers a wide range of input and output devices. Key concepts are clearly explained. The great thing about the BiteSize site is that it links to a series of related resources, including student activities, news article links, and online dictionaries and encyclopedias.

IGCSE ICT has notes on many topics (including input and output devices) that are useful for a range of ICT and Computing courses. The notes are very comprehensive, clearly divided into sections, well illustrated, and easily understandable for students. This is a good starting point for a lot of topics - not just for the IGCSE course.

TeachICT: detailed notes covering printers, screens, speakers, and more. Teach-ICT does have a range of activities for most topics, though they tend to be a bit gamey and only really appealing to younger students.

Covers all aspects of primary and secondary storage devices, including interactive lesson activities, notes, and a revision quiz. Well illustrated, this page also details the relative advantages and disadvantages of each storage medium.

Although targetted at the IGCSE ICT syllabus, this site still has a lot of useful information for other courses. Their section on storage covers different types of storage media and storage devices, including optical, magnetic, and solid state systems. They also have a section on backing up data.

Teach-ICT is a popular site which covers the basic topics of computer science - in this case, with notes on secondary storage devices and comparisons in terms of capacity, speed, portability, durability, and reliability. It also has a small section on online storage (cloud computing)

Logic Lab is a free online logic circuit simulator featuring many input and output devices, and even a propeller!

A revision video from Computerphile which covers the three basic logic gates: AND, OR, and NOT. The video includes truth tables, logic gate symbols, and the different notations that are used to denote 'AND' and 'OR'.