Online creation tools from Aviary Education

Aviary is a suite of powerful online creating and editing tools. The tools include an image editor, a color editor, an audio editor, an effects editor and an image markup tool.
They are all easy to use tools if you have a decent internet connection.

They have a special offer for educators. You can create private student accounts, manage assignments and projects, use the image editor, vector editor, audio editor & music creator and all content and images are 100% school safe.
The free account lets you sign up 50 students, so you could probably use it with one or two classes.