What kind of camera was used?

What kind of SLRs were used to take these pictures? I know there's a fish eye involved.
I myself have a Sony Alpha 100 (no fish eye). Planning to upgrade to a Nikon D90.
So, will I be able to take pictures of the same quality?

I love this one, is it more photo shopping than the camera?

There's one way that may help you. If you can get on that person's Flickr page, click on the photo in question. You should then have the option, under the "actions" menu to view the exif data.
On that list it should show the model of camera used. If that doesn't work, other than contacting
that photographer directly there's no way to find out.

I'd say it was a dslr of some kind because compact & bridge cameras don't do wide angle lenses.

You can do the fish eye in photo shop with what ever lens you have.
D90 has nothing to do with picture quality, its lens and composition and most importantly light. D90 will expand you further but A100 still can take these photos with ease.

First photo was found at showing the earliest date of April 11 2009

Second photo is at http://wallpaper.metalship.org/en/picture/-986.html

and the last one showing taken December 2ns 2009

None have EFIX information so no defined Camera or lens is known from the photos themselves. The first and last were taken from a previous websight and not by the flicker account holders. The second one is a Promo shot. All show signs of photo shopping.

Yes the D90 is able to do these shots, you can do a fisheye effect with the editing software in camera.

Yes you will. I own a Nikon D90 and the 10.5mm f2.8 fisheye and get the result of the first 2 images and better. While you can buy a fisheye for the a100 (sony has a wonderful system btw) like the 16mm or an off brand lens like a sigma 10-24mm.

The advantage the nikon has is it's low light ISO that holds up better than the low end models. However the image quality upgrade isn't that huge that you should buy a new camera over a more useful lens. Sony like Nikon and Canon offer pro models so you can upgrade to the top with what you have and opt for a good fisheye instead.

The last picture has a process called HDR (high dynamic range) applied to it. It is something done in post processing (aka Photoshop, Gimp or a software geared to doing hdr) and very few cameras can do it in camera. While the D90 is a great option consider your other options as you already have a solid base to start from.

The last 2 pictures obviously have had post processing so you might want to try getting a copy of photoshop instead and learn that skill.