I see that there's a new release of Paint.NET available (2.5α3). OK, so the name may be the most uninspiring since Windows Presentation Foundation (!) but this application is becoming more impressive with every release. Paint.NET is a comprehensive image drawing and manipulation package developed as an open source application using C#; it has many professional-level features including multiple layers, unlimited undo / redo, red eye removal, image acquisition, cloning, and magic wand selection. It's not quite a replacement for Photoshop yet, but it shows a great deal of promise and has come on hugely since its release. If you're building a Windows Forms application today, this is a great application to study as they've had to work through most of the major issues faced by any document editing application. Definitely worth a download - you've nothing to lose!