Hackpad is a new, simple wiki service that I learned about from one of Jackie Gerstein's Tweets earlier this week. People who have used services like TitanPad or PrimaryPad will notice a lot of similarities in the user interface between those services and Hackpad.
At the simplest level Hackpad can be used for collaborative note-taking and writing outlines. Beyond that Hackpad allows you to include video and images by simply copying and pasting links into the document that you're working on. If you have Dropbox files that you want to link to, you can do that on Hackpad too. The layout options on Hackpad are very limited, but you can create a table of contents with links in the margins of your Hackpad page. To organize all of the Hackpads that you participate in, you can create a Hackpad collection in your account.
There are two sharing options for your Hackpad pages. You can make the pages public and open to everyone with the link or the pages can be private and viewable only to the people you invite. Joining Hackpad can be accomplished by using your Google account, your Facebook account, or by creating a Hackpad-specific account.
Applications for Education
Hackpad's tag line is "the best wiki ever." I'm not sure that it's the best wiki ever, I'm still partial to Wikispaces, but Hackpad is quite nice. If you're looking for a clean, simple platform for your students to use to create outlines together, share notes, or build reference pages, Hackpad is definitely worth giving a good look.