Photo credit: Sebastian Kaulitzki

1. Zoho Viewer: Upload, view, and edit documents online, and get feedback from your team
2. Wizlite: Highlight text on any web-page, and let other people see and modify it
3. Weblin: Browser add-in allows you to chat in real-time with the people browsing your same web-page
4. Project Office: Manage projects, assign tasks, and create wikis to collaborate with others

1. Zoho Viewer
   
   Zoho Viewer is a new addition of the Zoho Suite, and it allows you to upload,view and edit any type of Office document online, enabling friends and colleagues to give you feedback. Without even registering, you can upload or provide a URL for your file (Word, Excel, PowerPoint, and PDF files), and start editing it online, wherever you are. You can then share it via email, IM, or by embedding it on a web-page, and allow people to give you feedback. Free to use.
   http://viewer.zoho.com/





2. Wizlite
   
   Wizlite is an online collaboration service that allows you to highlight text on any page on the Internet and to share it with anybody. You can create a group on Wizlite and share pages with their selections among a small group of people, and let them add their highlights too. It is available as a Firefox extension or simply a bookmarklet. It is free to use and requires registration.
   http://wizlite.com/





3. Weblin
   
   Weblin is a browser add-in, both for Internet Explorer and Firefox, that you can use to chat in real-time with people browsing your same web-page. After you download a small plug-in, you just have to register to the service for free, and you can then start surfing and chatting with people. The service is completely free.
   http://www.weblin.com/





4. Project Office
   
   ProjectOfficeis a web based online project management solution that enables you to collaborate with your team anytime, anywhere. Both individuals and teams can create projects and tasks, assign tasks to project members, track time, expenses and issues and create wikis to collaborate more effectively. The service is completely web-based and free. It requires registration.
   http://www.projectoffice.net/