Amium vs Dropmark: What are the differences?
What is Amium? Turn any file into a real-time activity feed and conversation. Amium turns every file into a conversation thread and activity feed. Files are synced and shared so you can work on them together and in real-time. Changes show up immediately in the conversation thread, and will also sync to your device.
What is Dropmark? Dead simple collaboration in the cloud. Dropmark offers super simple drag-and-drop file sharing, like a number of web apps before it, but if you want to use it for more you can create presentations, slideshows, and collaborate with others just as easily.
Amium and Dropmark can be primarily classified as "File Storage" tools.