XMind is the most popular mind mapping tool. Millions of people use XMind to clarify thinking, manage complex information, run brainstorming and get work organized. It couldn't be easier to get started.
A detailed list of features can be found here.
XMind is an open source project, which means it's free to download and free to use forever. XMind Plus ($79) and Pro ($129) with more professional features are also available.
It helps you keep track of project due dates, business meetings, etc.
Complex tool for creation of designs for circuits.
Idea organizer and note-keeper application.
Simple application that allows you to manage your to-do lists.
SWL is a free windowing and graphics package for Chez Scheme.