Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Standard Notes - A safe place for your notes, thoughts, and life's work
Event Hunt - Startups and Tech Events Curated By Locals
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets