Where can I get some nice sci fi textures

where can I get some royalty free sci fi, portal style textures?

I’m not sure what you mean by sci-fi portal, but I use:
http://local.wasp.uwa.edu.au/~pbourke/texture_colour/
Most of them are tileable.

And these are royalty free?

Also www.3dup.com has some neat textures.