Development-tools are very helpful. I give you a short list with useful web development tools which I use in my daily work:
- eclipse is one of the greatest development-IDE which I know.
- aptana plug in. Absolutely necessary for web developer who work with eclipse.
- git / svn plug-in. You know why...
- Build tool: ant. You can also use "make" but I prefer "ant" because it doesn't depend on an operating system.
- Acceptance tests: Selenium, Watir. I use Selenium but i read that watir should be a bit better... If you know more about please share your experience in the comments below.
- Debugging: Firebug-Plug-in and the build-in capabilities in google chrome.
- Performance: YSlow. Every web developer should know it.
- Continuous integration: Jenkins.