I just saw and downloaded a free new tool from MicroMat called MacProfile, available at
http://www.micromat.com/downloads/macprofile, which quickly answers basic questions about one's current Mac.
Things like the serial number and currently-installed RAM are fairly accessible from places like the System Profiler, but sometimes it is hard for normal folks to remember where to look. MacProfile combines the most-commonly asked technical questions in once place, and even includes such things as a machine's date of manufacture and maximum supported OS.
For those who are interested, more info at
http://www.micromat.com/downloads/macprofile