Host a Tree
They are a green web hosting provider who offers a good set of features at good prices. They offer both shared hosting and dedicated servers.
On shared hosting they offer .. instant setup of various web applications like blogging platforms .. email services including mailing lists ..
On dedicated hosting they offer, well, machines. For an extra cost you can hire them to manage the server. An interesting thing is the bandwidth is unmetered, but your machine is on a bandwidth-limited circuit.
To justify their claim of being a green web hosting provider, they purchase 100% renewable green energy to power their data center, web servers, office computers, laptops and office space. By purchasing credits to cover their entire equivalent energy consumption, they are assured of total energy consumption coverage.
They work with the Carbon Fund to evaluate and audit this program.