Yokohama is my "home town" when I visit Japan for work. True, it's not the most exciting place, but it's certainly pleasant enough. The Minato Mirai/Warehouse/Yamashita area is good for walking around at any time, and as mentioned earlier a baseball game is worth seeing if you haven't been to a game in Japan before. The Landmark Tower is worth it on a clear day, especially if you won't be anyplace else to catch a glimpse of Mt. Fuji.

I've done the curry museum and imagine the ramen museum is similar - nothing overly special but fine for lunch or a casual dinner. Plenty of restaurants of all kinds around, and I've had a good meal in Chinatown. Plenty of bars in Chinatown (as well as other places), with Rockwells and Ashes being the ones I get taken to most often.

My hosts tend to treat me very well when I'm there, so I haven't had much chance to venture beyond the Naka and Sumiyoshi/Minato areas to see what other attractions the city may have. As others have mentioned, it's convenient for a trip to Kamakura, and it's an easy trip to Tokyo should you have time to do some exploring there.