I found this is a very good site, site name : http://dmoz.org/
The Open Directory Project is the largest, most comprehensive human- edited directory of the Web. It is constructed and maintained by a vast, global community of volunteer editors. whenever you want a number of links on a topic, just go to it and have a number of links related to it, for example, if you want to know some links about operating system, see the result of the search. http://dmoz.org/Computers/Software/Operating_Systems/ click on specific topic and you will get a large number of links,, you can add some links also, and become a editor.
