I mainly use what almost everybody else uses. Photoshop 7.0 or Photoshop CS 2 depending on where I am at the moment.
Also, if you're not up for spending hundreds of dollars on this high end program, you can try Jasc's Paint Shop Pro. It is very good, I used to use it before I converted into Photoshop. It's basically ALL the same, layers, all the same filters but the only difference is the name. Even all the toolbars and palettes look identical but its not an illegal copy or anything. It is completely real.
I think the only thing its missing are those really really high end options in tools that the general consumer doesn't even use anyways.
Good luck on sig making
hone: