There isn't any real consensus on what Web 3.0 is as of the spring of 2012.

Suggested key features are:

• Data/Semantic Web - Inclusion of semantic content in web pages to promote common data formats.
  The semantic content will be in the form of metadata in web pages.
  Some standards for this include:
  Resource Description Framework (RDF) - Similar to classic conceptual modeling approaches such as entity-relationship or class diagrams
  and Web Ontology Language (OWL) - Allows applications to process the content of information instead of just presenting information to humans.
  

  See Tim, Lucy, and The Semantic Web - Web 3.0 | PCMag.com

• Personalization - Content customized for users based on their implicit behaviour and preferences.
  Keywords will be searched based on your culture, region, and jargon.
• Metaverse - Convergence of the virtual and physical world. e.g. Geosocial (Foursquare, etc.)
• The web as a personal assistant. At HowStuffWorks they suggest you will be able to ask "I want to see a funny movie and then eat at a good Mexican restaurant. What are my options?"

Real-Time Data

Collecta	collecta.com/	Monitors the update streams of news sites, popular blogs and social media, and shows results as they happen
OneRiot	www.oneriot.com/	Crawls the links people share on Twitter, Digg and other social sharing services, then indexes the content on those pages
FriendFeed	friendfeed.com/	A service which, instead of layering a meta-network on top of all your other social networks, will create a news feed incorporating them all. Users tell the feed which networks they belong to and FriendFeed personalizes a data feed with info from each of the sites.

Location-based Social Networking:
across networks and devices

Glympse	www.glympse.com/	A way to share your location with anyone for a specified period of time
GypSii	www.gypsii.com/	Connects people, places and communities
Wikitude	www.wikitude.org/	A mobile Augmented Reality (AR) platform