In the age of e-mail, you probably don't have a lot of need for the post office anymore. At least I don't. And yet I found myself recently in need of a money order (speeding ticket) and had no idea what to do--so I headed for the good 'ol post office on Park.
I was expecting long lines, unfriendly employees and generally a hassle. What I got was the exact opposite: multiple employees who were extremely helpful, no lines, and efficient service. I actually killed two birds with one stone and sent a package while I was there--all very easy and hassle-free, which was great.
So, yeah, don't be afraid to hit up the post office. It's night like going to the DMV anymore, apparently.