Universe Today Directory - Contains an hierarchical directory of thousands of web sites on astronomy topics.
Stardome - A concise set of links of special use to educators.
ilectric Metasearch - A fast and easy way to search multiple search engines. It collates and sorts the results according to relevancy.
Copernic - The free version of this software searches 18 major search engines, collates and sorts the results according to relevancy, and presents all of the results on one browse-able page. I have tried several meta-search facilities, and recommend this. It has a good ability to find hard-to-find pages, and is also very good at bringing the most relevant sites to the top of the list.
Link exchanges - Web sites that we have exchanged links with. These sites all have links pages.