Here's some different types of software and tools that I have found useful.
Marginalia - An Awesome Independent Search Engine!
Unobtanium - Search the web a little simpler
Stract - Cool idea with lots of optics like ' Remove the top 10,000 most popular websites from search results.'
Lieu - A search engine aimed at searching webrings. Useful mix of new and old discovery methods.
Search My Site -Only crawls user-submitted sites instead of trying to discover new sites.
Wiby - A search engine for websites using older technology, great for use on vintage computers.
YaCy - A decentralized search engine;
PeARS - A search engine that can be run in the browser, without needing a server.
Mojeek - independent search engine