Yeah extreme hills are really good, especially for building awesome things. I think next would be ocean biomes because it is just so awesome how is a giant open expanse of water, which is pretty awesome.
Flat areas next to anything, except desert. Have yet to find the benefit of a desert. But gotta have the flat area to have room to spread my builds out.
Snow farms are also handy, I use a snow golem one. I'll post a pic in a minute.