We don’t design and market in a vacuum, and these are some of the more useful tools that we’ve run into.
Website grader is a useful tool to benchmark basic aspects of your sites marketing and design. A score of about 70% can be thought of as adequate.
Google webmaster tools is a great way to monitor the health of your site from Google's perspective.
This is a great little swiss army knife seo tool for Firefox that allows you to look at things like in-linking, page rank, and more.
A fantastic online photo and image editing tool, think of it like an online Photoshop.