We love EFI. They are a nonprofit Energy Star Partner that provides lots of useful information and cares about the extra sustainability stuff like packaging and shipping to minimize impact (follow link and click on Sustainability Info on upper the left).
Depending on where you live, you can get Energy Star discounts and rebates at point of sale through EFI. At the bottom of the EFI site, look for the drop down labeled “Restricted Product Discount Offers” and see if your utility provider is listed.
They carry all sorts of products for saving energy and water. A bonus for us in Massachusetts is they have a brick and mortar store that you can visit as well, though we haven’t made it out there yet.
They provide lots of information about things like light quality, color and temperature explaining the full spectrum of things associated with choosing the right CFL. As they put it on the site:
provides information and products that can help you use less energy today.
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We have pruchased and received CFLs (including dimmables), low-flow showerheads, faucet aerators, weather stripping, and other air sealing materials from EFI. We are very happy with the products and the user experience.
Disclosure: We participate in the EFI Affiliate program so we do get some credit for purchases you make through the EFI links above.