If you are looking for a lenses to give you some super wide angles and great color, then look no further than the Sigma 8-16mm f/4.5-5.6 dc HSM.
This lenses is designed to give you great wide angle shots on a crop sensor. With up to a 114 degree angle field of view, you can stand immediately in front of a large object and get the entire image in one frame. This lens is especially suited for real estate photos where you are trying to capture the entire room.
The perspective that this lens gives brings new life into your images and this lens cannot be beat. On my Nikon D5100, when shooting at 8mm, I get a 12mm picture. In other words, you take the lens that you are shooting and multiply by roughly 1.5, so with my camera this lens is 12mm-24mm.
The size of the objective lens is large enough to gather a lot a light, so timed exposures at night are outstanding. I have included a picture above that was shot with the Sigma 8-16mm f/4.5-5.6 dc HSM on a moonlit night. As you can see, I am also using some lighting effects to give a sense of wonder to my picture.
I would highly recommend that you add this lens to your toolkit.