Word Processing:

• Google Docs
• ThinkFree
• Writeboard
  
• Zoho Writer
• gOffice

Spreadsheets:

• Google Spreadsheets
• ThinkFree
• Zoho Sheet
• gOffice

Presentations:

• Slideshare
• ThinkFree
• Thumbstacks
• Zoho Show
• gOffice

Calendars & Planners:

• Zoho Planner
  
• 30 Boxes

File Conversion:

• Zamzar - for example you can convert a document to a pdf file.

Miscellaneous:

• Google Sites - for creating a team site