I recently worked with a teacher that was teaching students about the different types of search engines and the uses of each. The focus was not so much on safe searches, but rather on the fundamental quality of the results, or the ease of combing through the results to find accurate and reliable sources for their research. Here are some search tools that were of note and some nice reminders.
InfoSpace created the Dogpile search engine because your time is important to us. Powered by Metasearch technology, Dogpile returns all the best results from leading search engines including Google, Yahoo!, and Yandex, so you find what you’re looking for faster. Each search engine has its own method of searching and each will return different results. Dogpile looks at all of them, decides which are most relevant to your search, eliminates duplicates and reveals them to you. In the end, you get a list of results more complete than anywhere else on the Web.
Reports results in category clouds and has tabs to categories by sources, type of site and time or how recent.
Mamma was originally introduced as the first metasearch engine in 1996 and earned the title "mother of all search engines" because it aggregated and organized the web's content from several of the leading search engines. It has continued to excel in this sector and also operates an Ad Exchange that provides Advertisers and Publishers an effective platform to obtain Internet traffic and generate revenue.
There's also good old Google, Google Scholar. Google Scholar searches the world of scholarly literature across many disciplines, ranks documents, and will let you build your own collection of links - your own library. Additionally, it's integrated into google docs and will even help with the citations.