Paint.NET.

Paint.NET, the free alternative to Adobe Photoshop and Corels Paint Shop Pro.

Paint.NET was originally designed to replace Microsofts Paint, which is built into Windows, but has grown way beyond its original purpose and is now released free under the Creative Commons Attribution Noncommercial licence.

Paint.NET is very intuitive to use, and we found it easier to learn from scratch than some of the aforementioned expensive packages out there on the market.

From the tabbed document interface which makes manipulating multiple images a breeze, to the Layer support normally associated with expensive alternatives, Paint.NET has many features which allow you to achieve professional results, without needing extensive training or tutorials.

Updates are released frequently, usually within 8 weeks.

My favourite feature is, without doubt, the unlimited history, which is a very quick and easy way to go back several steps, or even to the beginning of the project, to allow for both changes of mind, and genuine mistakes.