Planz is described as 'Keeping Found Things Found' and is an app in the office & productivity category. There are three alternatives to Planz for a variety of platforms, including Windows, Linux, Mac, Online / Web-based and Android. The best alternative is Dynalist, which is free. Other great apps like Planz are MemPad and Tkoutline.
Tkoutline is a single pane, cross-platform outline editor written in Tcl/Tk . With this editor, information can be structured hierarchically in an outline and outlines can be hyperlinked together to create a web of outlines.