1. EtherPad offers real-time editing and collaboration of plain text documents. It includes a mini chat room and shows each user’s edits with their own color in real time. Also nice is the ability to save and restore revisions. Here is a video demo.
2. Google Docs offers all three office apps for creating documents, spreadsheets and presentations. They also offer good sharing features which means you can collaborate with others in real-time at the same time on the same documents.
There’s also an option to post the document to a blog or website and have any changes updated automatically by itself. This makes it sort of like a wiki and a blog publishing platform. A downside to Google Docs is that you can’t chat with others inside Google Docs, but then again, you can always use Gtalk
3. ThinkFree provides a slick suite of online apps like Google Docs. You can use the web versions of their apps or install a desktop client that syncs with your online account which will allow you to work offline.Google claim to let you work offline via Google gears but you can’t create new documents offline, only view existing ones. Thinkfree allows you to do everything just like the full blown Microsoft Office suite.