For Google, It's a neat solution that mashes their News, Groups, and BlogSearch properties together with the more traditional finance information like profiles, earnings, financials, and trends.
The Flash powered trend graphs that link share price to news headlines is really neat.
As well as an overall market summary and exchange summary, Google provides an indepth page for each stock (here's GOOG). Again the price trend graph is linked to news headlines and is quick and easy to navigate.
Each page has a mashup of official company details (facts, summary, financial reports, and management team) along with more interesting information gleaned from Google resources -- such as Blog Posts, GoogleGroup discussions, related companies and news headlines.
Of course it wouldn't be a Google service if you couldn't log in, so they've provided you with an interface to keep track of your portfolio. It's quite straight forward, letting you add your stocks and the price you paid, and then listing your current values and profits/losses.
Update: Here's the official Google Blog entry.