Last week, Matt Johnson of Greater Greater Washington posted a system of three-character codes for identifying Metrorail stations. Shortly after that, BeyondDC published a similar system of two-character codes. However, as some commenters at Greater Greater Washington pointed out, WMATA already uses not one, but three distinct systems of station codes. Every Metrorail station is identified by one or more RTU codes, which consist of a letter, indicating the route, and two digits, indicating the specific station along that route. RTU codes aren't mnemonic, but they do follow a pattern (except for New York Avenue, since it's an infill station). Stations which are on more than one route (such as Metro Center) have more than one RTU code. In any event, there are two other sets of identifiers used by WMATA, and confusingly, they both use four-letter codes. One is used by MTPD, and the other by ELES.
So, with five different ways to identify a station, I decided to create a spreadsheet summarizing the various codes for every station. Personally, I'm going to stick to using RTU codes to identify Metrorail stations; from everything I've seen, WMATA employees are most likely to use RTU codes to identify stations, and given that there's no need to reinvent the wheel. But, if you want to compare the other systems of station codes, now they're all in one place for you to peruse.