Muse. I used it for visual organization of ideas. Right now iPad only.
Liquid Text. Best pdf for academics! Unbelievable features and visualization options. The paid version is worth the money… Please make a favor to yourself and try it. iPad and Windows.
Hook App. A nice way to find and relate archives, mail, pdfs… Only the paid version its useful (for me). Mac Only.
Zotero. A way to organize all your bibliography and study materials (even websites). There also nice integrations with other apps, like Liquid Text and Rabbit Research. Windows and MacOs, there are alternatives for mobile devices.
Rabbit Research. A nice place to find new bibliography. Right now web browser only.
Sololearn : learn basic programming
Why do I choose Apple products?