Makagiga is an open-source Java-based application which supports a vast number of functions.
The standard program has an RSS reader, to-do manager, text editor, simple calendar widget and more, and plugins can add extras like clocks, various web searches, an OpenStreeMap viewer, previewers for LaTex or Markbown/ BB Code, simple bar code generators, a thesaurus, screen capture tool and more.
There's no great integration with the operating system for any of this. The various functions don't live in desktop shortcuts, or dock to the edge of the screen: they're all accessed from Makagiga's own window.
Fortunately the program presents its capabilities well, and includes various examples to help you get started. A left-hand tree has various RSS feeds; clicking one opens it in a tab, for viewing; clicking other "examples" (Image, Link, Notepad, Todo) opens further tabs for those functions, and you can play around to see what they do.
Right-clicking one of the example tasks displays the main context menu, which provides even more clues. Here you can add new notes or to-dos, add RSS feeds, import data from elsewhere, or organise your data for easier management (give it a tag, color or rating, organise items in folders, and more).
Makagiga supports a lot of functions, so it's no surprise that some of them are very basic. But the RSS reader and to-do manager are equivalent to some stand-alone programs, the program also works well as a general organiser, and it's all highly configurable and extremely well presented. Worth a look.