Photo credit: Irina Tischenko

1. Screen2: Co-browse any webpage with other people while chatting with them
2. Zoho Share: Upload any document and let people annotate it for further sharing
3. ShiftSpace: Annotate and highlight webpages together
4. Anyvite: Create and share events with your friends via email, IM and SMS

1. Screen2
   
   Screen2 is a web based app that you can use to share your browsing sessions with anyone. Just enter someone's email, the website you want to start browsing and click: a pop-up window will come up, and you will be able to navigate any webpage being sure that the other person can see whatever you look at. Plus, you can also chat with viewers while browsing. Free to use, no registration needed.
   http://www.screen2.com/








2. Zoho Share
   
   Zoho Share is a document sharing service, part of the Zoho suite, that supports all Zoho’s formats, PDF files, Microsoft Office's documents, and other popular formats. After you upload a document, up to 3MB of size, users can grade, flag and comment them easily. You can then embed all of your documents in a viewer and share them on any site. Free.
   https://share.zoho.com/








3. ShiftSpace
   
   ShiftSpace is a browser plugin, which works in Firefox thanks to Greasemonkey extension, that anyone can use to annotate and editing webpages with others. When you are on a webpage, with a click of a button you can enter notes, highlight text, add images, and even edit the HTML code of the page, and make these changes public to anyone else who has ShiftSpace. The service is free to use.
   http://www.shiftspace.org/








4. Anyvite
   
   Anyvite is an online tool that lets you create and share events with people. You can create events in less than a minute by entering a title, description, time and location, and invite people via directly email. Recipients can reply directly to the email, without visiting any page, and they can be updated of any change via IM or SMS as it happens. The service is free to use and requires registration.
   http://anyvite.com/