Some great tools, lists and sources of inspiration that I find useful. And you might too!

Web Design

Color Scheme Generator - A good place to play around with different color combinations as well as useful information on the visibility of the colors to the general population.

Color Palate Creator - This tool allows you to work with different variations of the same color by adding white, black or whatever to a color base. Great for monotone color schemes of to help you find just the right shade of blue.

Lorem Ipsum Generator - When designing a layout that you don't have the content for this is just a generator of the bologna text to give the visual appearance of information on the page.

Color Tool - And yet another color scheme generator with some neat slider controls and allows you to see your colors in action.

CSS

CSS Zen Garden - A great place to learn about the power of CSS that features designs from a bunch of different talented artists via stylesheet manipulation. Participants are challenged to all use the same html document but are free to make changes to the CSS. The different variations that people come up with is quite interesting. This is also a great place to get inspiration when creative juices are running dry.

Search Engine Optimization

SEO Chat - This site has a bunch of tools that I like such as keyword density and future pagerank which gives a site's PR on all the different Google servers. There are also a number of interest articles related to SEO.

Keyword Position Checker - A good resource for locating your site in the top 100 search results of the major search engines.

Relationships of Search Engines - This is a nice chart for a bird's eye view of the information flow to and from the different search engines. Also some good information about the search engines themselves if you click on their icons.

Google

Matt Cutts - People with interest in the direction and current focuses at Google focus on this website. Matt works for the quality group at google and regularly discusses the search engine and it's fight against spammy sites.

Webmaster Resources

Standards Compliance - A resource to help webmasters validate their markup and assure quality code. You can also check the compliance of your CSS here.

HTML Character Codes - This is a great reference when you cant remember the numeric or character code for something like an é and you need to use the word café somewhere. It is also useful when making sure your pages are standards compliant.

Webmaster World - This is a webmaster forum that has been around for a long time and has a ton of active users and topics that span the gamut of webmaster interests. As with any other forum though, take any advice you see here with a grain of salt. Everyone there has an opinion on everything and opinions are like ... well you know how the rest goes.

PHP Date Formatting Codes - I always have to look these up to get them right.

Shopping Cart Software

List of different Shopping Cart Software - Here is a great list of most of the different software packages that are available with information including pricing, features and reviews.

Zen Cart - In my experience this is by far the best open source shopping cart available. With a dedicated team of developers, an active community and regular updates to their product they have quickly outpaced the other solutions I have tested. Best of all the software is FREE!

Other Useful Software

GIMP Image Editor - A great GNU image manipulation program and best of all it is absolutely FREE! Don't have hundreds of dollars to spend on the latest version of Photoshop? Then this software may be for you.

Tutorials

HTML and CSS tutorials - A few good, straight forward tutorials for people who want to learn HTML and CSS.