Dropmark offers simple drag-and-drop file sharing, like a number of web apps before it. But you can also create presentations or slideshows, and collaborate with others just as easily.
You can see the basic functionality of Dropmark in the video above, but here's a rundown. You create a collection of files, drag those files right into your browser, wait for them to upload, and then decide how to share that collection. You can make it public or share with individuals.
Depending on what you upload, you can use a collection as a (full screen) photo slideshow or presentation. You can even add video and entire web sites. You can also add music from SoundCloud and Vimeo and YouTube videos. If you'd like to see an example of a web site collection, the folks over at Dropmark created Choose Your Ipsum to demonstrate.
In the event you don't want to visit the Dropmark site to upload your files, you can just install a browser extension that'll bring up a sidebar you can use to quickly add files to any collection. Currently Chrome, Firefox and Safari are supported, but you can add a bookmarklet to other browsers as well.
Overall, Dropmark is a really fun and simple way to put together online collections of all sorts of things, whether that means files you've uploaded or various types of content from the web. When you sign up you get 250MB for free, but you can pay $US48/year for a 25GB upgrade.