Web 2.0 +



Google Docs and Spreadsheets offers collaborative tools that allow users to write online simultaneously.
NumSum is a web-based spreadsheet application where you can share progress reports, track reports, or any other number of things you could do with a desktop spreadsheet like Excel.
See Tip.
iPaper documents from Scribd are Flash widgets that you embed in your project. You can upload all types of files and view them right on your website.
See Tip.
Zoho Suites have productivity and collaboration applications similar to Google Tools.