Attached Link: http://www.debevec.org/Probes/

Mateo: the texture map is for the whole of the sphere. Actually, it doesn't have to be those proportions; if you look you'll see that the texture map for the preset shader of planet Earth is a square. And yes, you can apply the Environmental Lighting to a sphere of less resolution. That can be useful as the number of Anything Glows lights created for the standard primitive [about 260] can slow down the render time. kaom: HDRShop (which is free) will convert spherical hdrs to latitude/longitude. You can even use the program to make your own. All you need is a digital camera and a silver ball (such as a Christmas ball). One photo of a silver ball will actually give you a 360 degree panorama. There's a little distortion at the edge which HDRShop can get rid of with the help of a second photo but if you're not fussy about that, or the fact that you'll be in the photo, then one photo is enough. Picture number 1 shows a photo of my room reflected in a silver ball. Picture 2 is the Latitude/Longitude coversion done by HDRShop. This was saved as a jpg and then used for the Environmental Lighting in picture 3, rendered in C3. (If you look at the reflection on the sphere you can see the little amount of distortion, just left of centre.) I don't have any links to any really high res HDRs. But you can get away with a low resolution image if your main concern is the lighting and reflections. HDRShop will also covert the cross format to latitude/longitude and there are a whole lot of those at the link. The HDRShop site (link above) also has some in the tutorial section.