Here is a list of really cool demos for the HTML5 canvas tag. They probably won’t work for you unless you’re using an up-to-date web browser.

3D iPod Touch – There are a couple other demos on this page.

Canvas music visualizer

More to come when I get my bookmarks in order.

Virtuosi Media has a list of 37 regular expressions, each presented in javascript, PHP and perl formats. Includes regex for email address, URL, credit card number, phone number, ZIP code and more. I use this list all the time.

Statsy (http://www.phpied.com/statsy-more-data-points-for-markup-quality/) is a bookmarklet that does a quick DOM analysis of the page that you run it on. Tells you how much code you have inlined in your HTML, which I gather isn’t great for performance and can sometimes result in the dreaded FOUC.

Typetester (http://www.typetester.org allows you to fiddle around with CSS font settings until you find the right one for your site. You can adjust the font’s family (websafe and not), size, leading, tracking, alignment, word space, underline, color, background color and font weight, with a live preview on the same page. Once you’re done, the page will spit you out a list of CSS properties that you can paste directly into your stylesheet.

Also, the site’s design packs 3 testers onto the same page, so you can lay your fonts out next to each other and see how they work together. You can also use this to test alternative fonts for dimensional compatibility. Nifty!

MailChimp (http://www.mailchimp.com/ is my favorite bulk email sending service. Very simple. Just upload your email list, upload your HTML and send. It tracks detailed stats for all of your campaigns and holds onto them forever.

Litmus (http://www.litmusapp.com) allows you to test your websites or HTML email messages in practically every web browser and email client currently in use. You just put in a link to the site, or upload your HTML, and their engine renders the code in all the different programs and takes screenshots which you can easily flip through.

Unfortunately this service is not free, costing $50 a month, but it is well worth the price. Useful for web developers, indispensable for email marketers.

This website keeps track of all the email clients and how well they support HTML messages. Gives detailed lists of all the bugs for each, which can be helpful to reference when you are having a problem you can’t seem to fix. Very useful for email marketers.
http://www.email-standards.org/clients/