In writing some of my own software for both this blog and some commercial software I cant help but give credit to the many developers out there that produce free development tools and utilities. There are so many out there that we use I thought I would put together a list of a few that I use in my day to day work. By no means, is this a comprehensive list, its just some of the tools I use. Please provide comments if you wish to add additional tools.

1. Subversion ( Excellent open source version system if you cant afford TFS)
2. Toad  SQL (This is a free SQL management studio for various flavors of SQL servers. At last count they were supporting MS SQ Server, MySQL, Oracle, DB2) Even though each of these are separate its a must have if you are doing database dev. You can get the downloads here
3. Microsoft Powershell. This can be a very powerful utility if you use the SharePoint OM with it.
4. Powershell+. This is an awesome powershell IDE with breakpoints, script completion and a ton of over feature. A must have if you are using powershell.
5. #develop (SharpDevelop). Excellent free IDE for writing .NET code and SharePoint web parts.
6. CAML Viewer. A must have for any SharePoint developer. This makes CAML generation a snap and it is always in my toolbox.
7. STSDEV. Another must have for any SharePoint developer
8. WinMerge. Good tool for merging and diff'ing files.
9. FireBug (Great for seeing what stylesheets on in use on a SP site, but also great for allowing you to make real-time changes and visualize the impact.) Granted this is only a firefox tools, but i believe that IE8 will have something very similar.
10. Sharepoint 2007 Features Project. Some good developer tools that can be used in a dev rig. Items like logview, site actions menu that attaches to a debugger. There are some other items in this package so check it out.
11. WSPBuilder. Create project to help create WSP packages. Big improvement over how we used to have to create install packages.
12. SharePoint Manager. Excellent SharePoint object model explorer tool.
13. WSS 3.0 SDK. If your doing any development on SharePoint , this is a great resource, the only resource for many of us from the SharePoint 2003 days.
14. Sharepoint Server 2007 SDK. Another SDK resource.