I have a couple listed on my resume. I'm sure it helped get my foot in the door past the recruiting / HR shrews to get to an actual interview.
Was it worth the cost? Hard to say in the long run, but I think in the beginning it helped just a tiny bit to stand out from competition. They weren't all that costly to begin with, but at that time in my life, sure seemed like it.
As for further certs, push for the employer to pay for you getting them. Plenty of certs I never bothered to get, but studied for anyway just to stay ahead of the curve and keep my skills sharp.