I used to use these tools to develop my applications, I strongly recommend:
Microsoft Visual Studio .NET is a powerful IDE to develop easily desktop and web application. I use C# and VB as language and also is easy to work with database.
Full Versions: http://www.microsoft.com/visualstudio/en-us
Express Edition(FREE): http://www.microsoft.com/express/
Visual Studio Extensions
Spell Checker: http://visualstudiogallery.msdn.microsoft.com/7c8341f1-ebac-40c8-92c2-476db8d523ce
Go To Definition: http://visualstudiogallery.msdn.microsoft.com/4b286b9c-4dd5-416b-b143-e31d36dc622b
Microsoft Expression provide a bunches of products for the graphics and media world. I’m using Microsoft Expression Web that is like Dreamweaver focused to ASP .net technology.
More Info: http://www.microsoft.com/expression/
Gimp excellent image manipulation program. It is like Photoshop but FREE software (GNU) that was created initially for be used in Linux.
More Info: http://www.gimp.org/
Foxit Reader is not really a developer tool but is used to read PDF files. The main reason I chose it instead of Adobe Acrobat it is liter and faster. Foxit also provide PDF editor that is cheap compared to others. I recommend also the virtual printer PDF995 that is FREE to convert any file (doc, html, xls, etc…) to PDF.
More Info: http://www.foxitsoftware.com/pdf/reader/
The Fiddler web sniffer software is one of several well-known HTTP debugging proxies. It works well, and the proxy nature of the sniffer makes it stand out among other web sniffing tools. Ideal for: HTTP/HTTPS Traffic Recording, Web Session Manipulation, Web Debugging, Security Testing, Performance Testing
More Info: http://en.wikipedia.org/wiki/Fiddler_(software)