Reverse Dictionary - Describe a concept and get back a list of words
Sutle - Save and organize resources into a directed learning path.
Dictionary Anywhere - Dictionary Anywhere is an open-source and easy-to-use browser extension for Mozilla Firefox and Google Chrome that allows you to check definitions easily while browsing the web.
Golden - Mapping all human knowledge
Writefull Thesaurus - A Google Docs add-on that uses AI to give you synonyms
Gigasheet - The cloud spreadsheet built for big data.