Another of my Favourite Artists - Zdzislaw Beksinski (not for the squeamish)

http://www.metrocast.net/~stefburk/stuff/Beksinski - woah.jpg

Surreal, nightmarish, an absolutely obsessive attention to detail. His stuff looks so convincingly alien that it's almost hard to believe a human could've painted it. I first discovered his work in a SomethingAwful thread about creepy art, and this picture easily outdid everything else submitted. Other paintings of his popped up on the forums every now and then and the more I saw, the more I liked. He quickly became one of my favourite artists of all damn time.

Here's some links (obviously don't click if you're easily offended/disturbed):

Official Site - Lots of stuff but the images are kinda small and take awhile to load (at least they did for me); requires Flash.

Gallery 1 - Pretty respectable gallery, high-quality images, some of them fairly large.

Gallery 2 - Large gallery, medium-sized images of mixed quality. Includes a few pages of his digital art.

Gallery 3 - Nice collection of both paintings and computer graphics. Small but high-quality images.

Gallery 4 - Small gallery; again, small images but high-quality.

Gallery 5 - More from the same site as Gallery 4.

Gallery 6 - Big gallery of tremendously varying size and quality, some paintings, lots of digital.

Wikipedia Article

Feel free to add to the list if you have links to any of his work not posted here. Hope you enjoy!