A meta-search engine a little like Searx. Not as featureful, not many features, but for something quick and dirty to just get stuff done it seems to do the job. No Javascript. Self hosted. Strips tracking codes out of URLs it finds. Lightweight - no Composer stuff, all self contained. Has an API but not REST.
A meta-search engine for ecommerce sites. Search for something to buy and get links to multiple sites where you can get it. Search a particular country, or search globally.
A search engine for public records archives and sub-searches around the country.
A directory of public Searx instances.