What Tokyo ramen site would be complete without mentioning Ippudo. The Ebisu Ippudo (technically it is in Hiroo) is a branch of a well-known Hakata-style tonkotsu ramen chain, actually that chain's first branch in Tokyo. They have a broth that is not *extremely* fatty but still has a rich taste (it is very salty though). Since I work near the Ebisu branch I find myself in there (with my coworkers) for lunch about once or twice a month. At this and pretty much all Ippudo locations that I have been to, you get free spicy moyashi, karashi takana (spicy greens) and shoga at your table to eat on your rice or on your ramen. The Ippudo shiromaru or akamaru lunch sets (ramen, gyoza and all-you-can-eat rice), for 750 yen at the Ebisu shop, are probably one of the best deals in town, along with the special "African tea" pitchers at each table. The akamaru is a slightly stronger flavor, I recommend the shiromaru but they are not that different. My personal recommendation is to ask for the noodles to be "katame" (somewhat firm), although you can get them extremely hard "harigane". A couple of months ago they also introduced an "ultimate" version of the akamaru, called kiwami shin-aji, with some suspended egg in the broth, a bigger portion, and a side dish consiting of a strange cube of a miso-like substance which I believe was meant to be mixed into the broth to your own taste. This ultimate version was 1300 yen and was good but wasn't worth the extra cost IMO. Also the waitstaff at this location is used to foreigners and is very friendly, although they are very rushed too. Chances are you will wait on line if you go between 12 and 1 PM. If you are visiting Tokyo for the first time and you only have time to go to one ramen shop while you are here, this would be my recommendation.
Also of recent interest is the announcement that Ippudo will be opening a branch in NYC: http://intertrend.com/wordpress/?p=387
2008-03-16 - UPDATE - Ippudo has switched to slightly smaller platform bowls (agesoko?, third picture above) so the base soup amount has gone down, and the price also recently went up to 850 yen. And they don't give you a stick of gum anymore. However everything that was tabehoudai before still is (rice and veggies), and it looked like the buta slices were a bit bigger and thicker. Still my area recommendation though.
2008-3-28 - ANOTHER UPDATE - Here is the flyer that they are handing out in Tokyo to advertise the opening of the new Ippudo in New York City:
Ebisu Shop Page + Address
Ramen Road Review
Diddlefinger Map (English labels)