Este es un set de herramientas Web que siempre tengo a mano. Espero le sirva a alguien más

Flex Style Explorer: Sin dudas un pedazo!!! de herramienta para la creación de CSS. Gracias Mimolu por enseñarmelo

Em Calculator is a small JavaScript tool which helps making scalable and accessible CSS design. It converts size in pixels to relative em units, which are based on a text size.

Firebug: Web Development Envolved integrates with Firefox to put a wealth of web development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.

The Web Developer extension adds a menu and a toolbar to the browser with various web developer tools. It is designed for Firefox, Flock, Mozilla and Seamonkey, and will run on any platform that these browsers support including Windows, Mac OS X and Linux.

SeoMoz

SeoTalk

swfobject

popuri.us: A tool to check at-a-glance the link popularity of any site based on its ranking (Google PageRank, Alexa Rank, Technorati etc.), social bookmarks (del.icio.us, etc), subscribers (Bloglines, etc) and more!

CSS Formatter and Optimiser: Herramienta muy interesante para webmasters, se trata de Clean CSS, una herramienta online que nos limpia nuestro CSS. Esto se logra eliminando ciertos parámetros innecesarios

URLinfo is a tool for handling web pages: finding information about it, translating it, finding related pages, etc. To use it, type a URL (web page address) into the box in the top frame. Then choose a tab (such as General or Cache), and click on the name of the specific tool you wish to use. The Translate and Search tabs require a bit more, but should be self-explanatory. Click on the [info] link at the end of any tab for details about it. URLinfo includes 113 tools.

SiteMaps para Google

What The Font

snif: simple and nice index file

Constructor de Layout´s: crear layouts de forma sencilla

examinator: Revisa y evalúa la accesibilidad en la web

bubbl.us: Brainstorming 2.0

pic2color.com: Extrae los colores de todas las imágenes

favicon2dots.com: Favicon en 3D

Favicon From Pics: Herramienta para crear nuestros favicon

krugle.com: Buscador de Codigos

dnscoop.com: Averigua todo sobre tu dominio

robtex swiss army knife internet tool: rbls, ipnumber, hostnames, domainnames, whois lookup, c-net, route, as numbers, bgp announcements, as macros, rfcnumbers

…si te sirvio alguna cuentamelo