Tired of missing the bus or watching it go past when you're still a block away? I sure am. It looks like there may be a solution - Nextbus has a website for WMATA which has a scheduler and a cool live map function, pictured here. However, it seems like a beta version, as you can't get there from the main Nextbus page, and it's not listed on the WMATA website (their site says it's offline). But if you go to the link above, it works.
I haven't checked the accuracy of the site yet, but it looks cool - you can pick a line, pick where you are and where you're going, then see when the next three buses show up. Once you're at that page, you can click "Live Map" to see where the buses actually are, both northbound and southbound, and it updates as they move - here's the direct link. You can also add more routes (for example, the 52, 53 & 54) - click "Routes" and add the ones you want. (The Google Map option seems to be broken.) If you put your mouse over a stop, it will show you what lines service it and when the next three buses for each line will come.
This is potentially really awesome, so I'll let you know if it works on my trip home today.