By listening, reading, and participating, brand marketers have an opportunity to make their brands more approachable and shareable than ever before. There are many tools available to us for listening, both free and those that require subscriptions, which will reveal the conversational hubs that require our attention.At the moment, the tools are mostly specific to each category of social media as well as specific networks.

Social Bookmarks
Ma.gnolia
Delicious
Diigo
StumbleUpon

Crowdsourced Content
Digg
Yahoo Buzz Mixx Hubdub Reddit
Newsvine

Blogs/Conversations
Google Alerts Blogpulse Radian6 (paid) BuzzLogic (paid) Ask.com
Google Blog Search Technorati

Blog Communities
Blogged.com
MyBlogLog
BlogCatalog
Bloglines
CoComment
Tangler

Micromedia
FriendFeed
Pownce
Tumblr
Seesmic
Jaiku
Plurk
Utterz
Pinger
Jott
Kwiry
Twitxr

Specific to Twitter:
Tweetscan
Hashtags.org
Summize
Twemes
TwitterLocal

Social Networks
MySpace
Bebo
Facebook

Niche Networks
Ning Plaxo Linkedln CrowdVine

Location
TriplT
Dopplr
BrightKite
TwitterLocal

Live Video and Audio
Ustream Justin.tv Veodia
BlogTV Kyte
Qik
BlogTalkRadio

Customers Service Networks
YahooGroups
GoogleGroups
GetSatisfaction
Yelp

Video
YouTube Metacafe
Blip
Viddler

Video Aggregation
Magnify.net

Pictures
Flickr
Zooomr
Smugmug

Documents
ThinkFree Docs
Scribd Docstoc

(Source: http)