The Best Free SEO / Usability / Site Speed Analysis Tools
The Best Free SEO Site Analysis & Optimisation Tools
Screaming Frog SEO Spider Tool & Crawler Software
http://home.snafu.de/tilman/xenulink.html - will give you broken links as well as an export of images missing alt text.
http://try.powermapper.com/demo/sortsite.aspx - there is also a free 30 trial day of a version that will allow you to analyse up to 100 pages from a site.
http://builtwith.com/- Find out the technology behind a website
http://suite.searchmetrics.com/en/research - view data on search visibility for a domain and key phrase / domain.
http://www.copyscape.com - Search for copies of your page on the web.
http://www.siteliner.com/ - Explore your site's duplicate content, broken links, XML sitemap, internal page rank, and more...
http://sitebeam.net/ - Sitebeam tells you about a website. Scan 10 pages for spelling mistakes, SEO, load speed, social media, code, W3C, accessibility & more in one tool.
http://www.found.co.uk/seo-tool/ - A free online tool to identify common SEO errors with a webpage including canonicalisation, technical implementation & link lnformation
The Best Free Usability Analysis & Optimisation Tools
http://www.feedthebot.com/tools/alt/ - Tool to help make sure that your (image) ALT attributes are descriptive and accurate.
http://www.contentquality.com - includes an Alternative Text Quality Report.
The Best Free Site Speed Analysis & Mobile Optimisation Tools
pagespeed.googlelabs.com - includes a mobile Site Speed Analysis Tool
http://www.webpagetest.org/- Run a free website speed test from multiple locations around the globe using real browsers (IE and Chrome) and at real consumer connection speeds. You can run simple tests or perform advanced testing including multi-step transactions, video capture, diagnose slow servers ( a time to first byte of >0.2s), content blocking and much more. Your results will provide rich diagnostic information including resource loading waterfall charts, Page Speed optimization checks and suggestions for improvements.
http://www.howtogomo.com/en-gb/d/test-your-site/ - this tool shows you how your current site looks on a smartphone,
http://www.gtmetrix.com - uses Google Page Speed and Yahoo! YSlow to grade your site's performance.
Czech out http://twitter.com/SEOTipsnTricks for some more free SEO Tips, Tricks, Tools and more...