Assembly is a language, there is at least one for every instruction set.
Yes, absolutely put it on there even if you write web applications in a high level scripty language.
Maybe where I work is the exception not the rule (the networking business, and chip/processor business) but a fair amount of our programmers know and write assembly, and even if you were looking for a linux porting or device driver job we would see the assembly experience, ask you questions about it and make decisions based on your answers.
Like anything else on your CV that doesnt relate to the job you are applying for they will just skip over it. this is not a "less is more" kind of thing. If you really know something put it down, languages, processors, protocols, apis, etc. If you leave things out and expect the interviewer to read your mind or be forced to guess at what questions to ask to try to draw this stuff out, it is to your disadvantage. I would rather have a multi page CV/resume to look at when interviewing a candidate than someone who tried to cram what they could on one page and left out the "meat". Often a resume like that doesnt make it through the pre-screening process. HR often scans the resumes for key words, enough key words and you rise to the top of the pile, not enough or none and you get discarded without even a phone interview. Instead of less is more, more is more. At the same time if you dont really know the language, or took a class in it in college and it was so long ago you really dont remember any details, leave it off, getting to the interview with answers like that encourages your resume/CV to make its way quickly to the shredder.
Yes list it as a programming language, that is what it is and specify the processor (family).
C, C++, Java, assembly language (x86, ARM, MIPS), Python, Perl...
Some folks will list the assembler not the language TASM, NASM, MASM.