Gizmo's Freeware is a site that has a great list of online free apps. I'm a huge proponent and user of free apps and web-based apps. They are free, easy to use, and the online ones are available anywhere.
The article has a huge number of free online apps, organized by category, with a short review. It's a great place for educators and students to find some very useful, and free, apps.
Categories include: office suites, PDF tools, document viewing and sharing, notebooks, to do lists, and much more.
Check it out!