A web hosting provider offering a fairly comprehensive set of features in shared hosting plans. Their servers run Linux, offer PHP with Zend optimization, and a useful set of available features.
They also offer managed dedicated servers.
Their claim to being 'carbon neutral' is through purchasing Green-E Certified power. They show the certificate on their site, and they buy credits equal to 40,000 kwh of power per year. They also note that until we have properly recyclable computers there will be no such thing as truly sustainable web hosting.