list.it is described as 'simple, free, open-source (MIT-license) note-keeping tool to help you manage the tons of little information bits you need to keep track of each day. Installs as i Firefox add-on' and is an website in the Office & Productivity category. There are more than 100 alternatives to list.it, not only websites but also apps for a variety of platforms, including Windows, Mac, Android and iPhone. The best alternative is Joplin, which is both free and Open Source. Other great sites and apps similar to list.it are Standard Notes (Freemium, Open Source), Google Keep (Free), Microsoft OneNote (Freemium) and Evernote (Freemium).
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, can be copied, tagged and modified either from the applications directly or from your own text editor.