The American Association of School Librarians publishes a list of the Best Apps for Teaching Annually. Check out the websites on this year's list, or look at those from previous years. AASL chooses its best websites based on those that teachers recommend. Websites are organized into categories to make them easier to navigate, this year's categories include:
Some apps on the 2014 list include:
Level: Early elementary (K-2)

The fuzzFamily crashed their spaceship on Smeeborg and need your help to explore the planet's Technomazes. Use your finger to drag and drop instructions for your fuzzes to follow. Then hit Play to watch them roll through the maze with curiosity. BEWARE: Fuzzes are very LOGICAL and will follow every command exactly as you tell them! Get rewarded with stars, coins, and even EXTRA members of the fuzzFamily as you successfully complete mazes.
Tip: Use step by step sequencing to help young students master programming logic.
Level: Early elementary (K-2), Upper elementary (3-5), Middle school (6-8), High school (9-12)

Capture learning in a e-portfolio using Easy Portfolio. A variety of artifacts including videos, pictures, audio files, links to external sites, and documents can be saved to a student's portfolio.
Tip: Students can save examples of their work in order to participate in student-led conferences.
Level: Early elementary (K-2), Upper elementary (3-5), Middle school (6-8), High school (9-12)

Tellagami is a mobile app that lets you create and share a quick animated video called a Gami. To create a Gami, customize your character and background, then record or type a message for your character to say.
Tip: Students can customize their own avatar, upload images for backgrounds, and record their own voice to create their Gami. No account or login information required.
And many, many more. Check them out yourself on the AASL Best Apps for Teaching and Learning 2014 blog: http://www.ala.org/aasl/standards-guidelines/best-apps/2014