This article contains a list with some free online tools I found very useful for my daily work. Even if you are a developer or a designer, these tools can realy improve your work.
Color Scheme Designer is an easy to use and efficient tool that can help you choose color schemes for your designs.
Similar to Color Scheme Designer, Adobe Kuler is an internet application from Adobe that lets you create and save various color schemes.
Typetester is an online application for comparison of the fonts for the screen. Its primary role is to make your life (as a web designer) easier when dealing with web fonts.
Pixlr is a free online photo editor. If you just need something to edit, adjust or filter your images, then Pixlr is the tool you're searching for.
Browsershots is an online web application that provides developers a convenient way to test their website's browser compatibility in one place. It can help you to make screenshots of your web design in different operating systems and browsers.
Pingdom offers an online tool that can help you test the load time of a web page. Just enter a URL and test the load time of all elements on that page.
About the W3C's validator tool there isn't too much to talk about. As you already may know, this checks the markup validity of web documents as HTML or CSS.
This isn't really a tool, but Iconfinder is a must-have. Just consider it as your number one "search tool" for free icons.
As its name says, Code beautifier is a CSS formatter and optimiser tool.
Need an online place where you can test your CSS3 skills? Then here's your playground!
As a conclusion
Did I mention the above tools are FREE? Yep... they surely are! Thanks for reading this article and please let me know what other online tools you are using!