Wapiti allows you to audit the security of your web applications.
It performs "black-box" scans, i.e. it does not study the source code of the application but will scans the webpages of the deployed webapp, looking for scripts and forms where it can inject data.
Once it gets this list, Wapiti acts like a fuzzer, injecting payloads to see if a script is vulnerable.
Nikto is an Open Source (GPL) web server scanner which performs comprehensive tests against web servers for multiple items, including over 6500 potentially dangerous files/CGIs, checks for outdated versions of over 1250 servers, and version specific problems on over 270 servers. It also checks for server configuration items such as the presence of multiple index files, HTTP server options, and will attempt to identify installed web servers and software. Scan items and plugins are frequently updated and can be automatically updated.
CSS Lint points out problems with your CSS code. It does basic syntax checking as well as applying a set of rules to the code that look for problematic patterns or signs of inefficiency. The rules are all pluggable, so you can easily write your own or omit ones you don't want.
JavaScript is a class-free, object-oriented language, and as such, it uses prototypal inheritance instead of classical inheritance. This can be puzzling to programmers trained in conventional object-oriented languages like C++ and Java. JavaScript's prototypal inheritance has more expressive power than classical inheritance, as we will see presently.
Online validator for iCal files
This website and its sample code creates a template of sorts, absent of design or layout, that will help you avoid some of the major rendering problems with the most common email clients out there — Gmail, Outlook, Yahoo Mail, etc. While not plug and play (you know, you'll have to do some work ;-), it will provide some helpful examples and snippets that will keep your email design rendering as true-to-form as possible.
The PHP micro-framework based on Symfony2 Components
Your favorite site doesn't provide news feeds?
This free online service converts any web page to an RSS feed on the fly.
Maqetta is an open source project that provides WYSIWYG visual authoring of HTML5 user interfaces. The Maqetta application itself is authored in HTML, and therefore runs in the browser without requiring additional plugins or downloads.
To help you find the perfect CSS-reset styles, CSSresetr lets you try all the best CSS Resets on a variety of web pages – even your own.
HTML5 <video> and <audio> made easy.
One file. Any browser. Same UI.
Streeme can serve music to most HTML5 compliant browsers and smartphone handsets using the computer you already own.
History.js gracefully supports the HTML5 History/State APIs (pushState, replaceState, onPopState) in all browsers. Including continued support for data, titles, replaceState. Supports jQuery, MooTools and Prototype. For HTML5 browsers this means that you can modify the URL directly, without needing to use hashes anymore.