Search Engines &
Web Directories

Directories (sites chosen by humans):

Librarian's Index to Internet
Search tool for quality websites that have been evaluated by librarians.

Internet Public Library
IPL is the first public library for the Internet. Contains quality websites that have been evaluated by librarians.

Dewey Browse
Search for websites using the Dewey Decimal system of classification.

Search Engines (sites found by machines): 

Google

Yahoo

These search engines are subject specific: 

Daypop
A Current Events Search Engine

Technorati
A Blog Search Engine

Opinmind
A Blog Search Engine

Related search tools:

TalkDigger
Enter in a URL and finds what sites (from a variety of different search engines) are linking to it.

Noodle Tools
Use this chart to decide which one to use for your type of search