Vector graphics software is used to create artwork that can be re-sized without any loss of quality. Adobe Illustrator and CorelDraw are the two most widely used examples of this kind of software.
Commercial graphic editing software can be very expensive. The list below contains open source or free alternative graphic design software.
Paint.NET (PC only)
This software was started as part of a college project and has continued to be developed. Paint.NET can be enhanced with the use of plugins. Paint.NET only works in Windows. A user manual is available.
Pinta (Mac only)
Pinta is like Paint.NET except it is for Macs.