Feedback Loops:

Most searches occur at the main search sites and portals (Google, Yahoo!, MSN, AOL, etc.), but some people also search for temporal information, looking to find what is hot right now, or seeing how ideas spread. Not everyone can afford WebFountain, but we can all track what people are searching for or how stories are spreading using:

Feed Readers :
Subscribe to your favorite channels (or topical RSS feeds from news sites)

Blog Search:
search for recent news posted on blogs

Blog Buzz Index:
search for stories rapidly propagating through blogs

BlogPulse
PubSub
Technorati popular news popular books
Daypop top 40
Bloglines top links site readers public profiles related feeds
BlogDex
Findory
Start.com
Memerandum Tech
Blogniscient
Blogmarks
Ice Rocket brand A vs brand B
Topix.net Blogs

General Buzz & Search Volume:

Buzzingo
Yahoo! Buzz Index overall
Lycos 50
Google Zeitgeist
Google Suggest
Google Keyword Tool - shows 12 month historical trends!
Overture Search Turm Suggestion tool View Bid Tool
my keyword research tool - like Overture's, but it cross references many of the ideas on this page - like tagging, etc.
Amazon best sellers
TrendWatching

Product Feedback:

eBay Reviews
Become.com shopping search
Yahoo! Shopping
Clickbank ordered by purchase volume & price
Amazon feedback
Google Groups
forums (see Boardtracker)
general search

News Search:

Akamai net usage index - check general search volumes
Google News RSS
Yahoo! News (with blogs) RSS
Topix (with blogs) RSS
Gixo
NYT most emailed articles
Wikipedia most edited talk pages (controvercial stuff)
Newsmap (just plain cool)
Newsingo
Findory

Test Ad Accounts & Test Media:

Google AdWords
Yahoo! Search Marketing
write press releases and submit them cheaply to see how much buzz & news search volume their is around a topic, using sites like PR Web or PR Leap
post on a topic

see if it spreads
check referrer data
Sometimes stories emerge out of the comments. The Save Jeeves meme that spread originated around the time the person who created that story commented on my post about Jeeves getting axed.
Don't forget to have friends tag your story on Del.ico.us and submit it to Digg.

Tagging:
Some are busy tagging what information they think is useful.

Delicious - personal bookmark manager.
Wink - tag search
Flickr - image tagging hottest tags
Tag Cloud - shows graphic version of hot tags
Furl
Technorati Tags
Digg Top Stories
Reddit
Ning
Squidoo
My Yahoo!
Google Search History (you can't see what others are tagging, but I bet it eventually will influence the search results - Google is already allowing people to share feeds they read)
more tagging sites come out daily...lots of others exist, like Edgio, StumbleUpon, Shadows, Kaboodle, etc etc etc
also look at the stuff listed in Google Base...there may or may not be much competition there, and Google Base is going to be huge.

Track Individual Stories and Conversations & Trends of a Blog:

Bloglines who cited this post
Technorati links pointing at a URL
Blogpulse Conversation Tracker
Technorati and Blogpulse also allow you to track how hot a word or phrase is in the blogosphere over a period of time.
- Technorati "Aaron Wall"
- Blogpulse "Aaron Wall"
Pubsub allows you to create a feed for a brand or product name or issue.
CoComment - allows you to track comments