For example (just as rough proof of concept)
Research articles: Pretty much any academic library website for published stuff, arxiv.org for white papers in computer science and math, pubmed for biosciences
audio equipment: gearspace.com
Encyclopedia: Wikipedia
Thesaurus: Wordhippo.com
The idea is to avoid needing to visit a search engine. Might be a high idea.
God I miss a well tended DMoz.
And then when Google copied it and sorted category links by PageRank? The good old days.
DMoz’s not well tended successor is Curlie.