OSDev.org

hi,
I wondered which assembler is the best?

Depends on your taste, if you prefer AT&T syntax, go for GAS, otherwise I would recommend, in order: FASM (this one was specially designed with OS devel in mind, and is self compilable, so it's a huge plus), NASM, YASM.

Assemblers are like religion - you take one and you believe in it.

Tool Comparison

I like Fasm because its syntax makes more sense to me. But it all depends on what you like, I suggest looking around and comparing there syntax to see witch one you are more confertible with using

I blend NASM and GAS. Mostly because I never bothered to actually learn the syntax of any one assembler, and I know considerable chunks from both, so what I don't know in one, I most likely know in the other. It's like a buffet table for me.