Snippely - Snippely is a basic text and code organizational tool.
Zeal - Zeal is an API Documentation Browser.
Devhelp - Devhelp is a GTK+/GNOME browser for API documentation; it works natively with gtk-doc (which is the...
SnippetsLab - SnippetsLab is an easy-to-use snippets manager.
Quiver - Quiver is a notebook built for programmers.
LINQPad - A scratchpad for C#, F# and VB code including Linq queries.