Don't forget that one of the first ways to limit your searching is to think about the type of content you want to find. Yahoo!'s and Google's news pages are a great way to browse or search through current news articles from reliable sources worldwide.
Look for the links that let you search only on blogs, audio, video, images, and other types of content.
Google has a book search feature that lets you search the text of books that they have scanned - this is a massive and controversial project. Their catalog search lets you search online catalogs.
Another great place to start can be Answers.com. They collect content from authoritative resources, plus wikipedia, and present it in one page, complete with citations.
News
Pictures
Other types of content - blogs, etc.
Multimedia