I finally did it...I bought the Sigma 10mm f/2.8 fisheye today (tax free)...and am already lovin it.
This is the Old Danvers State Hospital Main building that has now been converted to apartments. this is a perfect building for my first fisheye photo. The sky was a perfect blue, but because the photo is funky anyway I decided to play around with shadows and highlights and saturation just a bit. (double click on the photo for better quality view)