For Google, you may select New York Times feed offered as an example, search for [Google blog] or enter the address of this blog: googlesystem.blogspot.com. Google Finance lets you filter the posts from the selected feed using the "search within items" option. There's even an interesting trick that lets you plot some custom events on the chart. "Google Spreadsheets can be treated as RSS feeds and plotted on a chart. Just make sure your document contains a date column and some basic formatting, and that it's published to the web." Here's an example of spreadsheet plotted in Google Finance.
If you want to obtain a permalink for your custom chart, click on "Link to chart" and copy the address. Unfortunately, you can't save a list of feeds or connect them with certain companies.
{ Thank you, Alexis K. }