Using a P.S. in a cover letter?

No. A P.S. was used to indicate an afterthought (oversight, clarification) when typewriters were used and you couldn't go back and delete something or add something in. You're typing this on a computer. A P.S. would just look silly and unprofessional. If you want to grab the hiring managers attention be short, clear, and to the point. That way, they actually read your cover letter instead of skimming it and tossing it aside because there's too much written. Include one or two areas points of actual evidence (try to include numbers) that you think make your resume worth looking at further. Be professional and have at least 3 people read it for errors. If you know the hiring managers name, use it rather than "To whom it may concern". You can also use wording that indicates you're confident in your abilities/experience and that you actually see yourself working there. That will also help set you apart. You can add at the end that you plan to call them by x date to set up a convenient time to view the facility. Make it a week or so from when you send your resume and then ACTUALLY CALL THEM. Some people says that this will back fire and if they wanted you they will call you, but I've never actually heard any first hand evidence of this. Anyone that I know that has done this, has gotten an interview (not necessarily the job, though). Whatever you do make sure you keep it short and to the point.