DIA - Engineering diagrams

1. Dia is an application for creating technical diagrams. Its interface and features are loosely patterned after the Windows program Visio. Features of Dia include multiple-page printing, export to many formats (EPS, SVG, CGM and PNG), and the ability to use custom shapes created by the user as simple XML descriptions for generating the desired code. Dia is useful for drawing UML diagrams, flowcharts, database diagrams, network maps, electrical circuits and many others. 
You can download for free:
http://projects.gnome.org/dia/



2. BlueJ is an integrated Java environment specifically designed for introductory teaching. BlueJ supports:

• fully integrated environment
• graphical class structure display
• graphical and textual editing
• built-in editor, compiler, virtual machine, debugger, etc.
• easy-to-use interface, ideal for beginners
• interactive object creation
• interactive object calls
• interactive testing
• incremental application development 

Downloadable from:
http://www.bluej.org/download/download.html