We just bought about a month and a half ago, and we used an agent. Trying to keep up with what's actually available through the various websites turned out to be a bit of a pain. In the end, it actually didn't matter since we ended up building, and not buying an existing home, but after having gone through that I would strongly recommend you get yourself a good realtor that's familiar with the area you are interested in.
And it's been my experience that many of the realtors around here specialize in fairly small regions, so if you get an agent that really knows say, Prince Fredrick, that same agent will probably not be very familiar with Great Mills. So find where it is you want to be, then find someone that really knows that area to represent you.