There are several websites which can be very handy for people who want to optimize a website. Here's a list of the websites I use.
This is the website of Simon Kloostra, wellknown of his SEO- en and speed up your site knowledge. On his site he explains which steps you can teake to optimize your own site for SEO or making your website faster.
You can scan your website here for pointers of the Google Webmaster guidelines. Besides this there are also lots of interesting articles about enhancing your website.
On this website you can scan your website on some technical performances, after the scan you will be given the score and some information on what you can do to optimze. Also interesting is the Yslow and waterfall measurement of your website.
A brief scan of your website can be performed here. You also have the choice in selecting the server from where the scan will be performed. If you have a Dutch website for instance, it's not usefull the scan it from the USA but it is from Amsterdam.