This is the only large Asian supermarket I know of near me, and it's in Van Nuys, which is not that near (they have many other locations, too--check out their website to find them). The store not only carries just about anything you could possibly want, they have a variety of brands for most items. I particularly noted their ample selection of fish sauces and ice cream (including a wide variety of soy ice cream). I am also very pleased with their selection of produce (kaffir lime leaves, very fresh peeled garlic, galanga, pretty much anything you could want), canned fruit, curry pastes (Mae Ploy brand is the best), canned drinks, and bamboo plants. If you're looking to make your own stir-fries or tacos, you'll be thrilled with their selection of meat that's already been cut for just this purpose.
One thing I have not been able to find here, and oh, how I have looked, are sesame balls with red bean paste on the inside. I like to buy a big bag of them, frozen, and cook them individually in the toaster oven. 99 Ranch only sells them individually in the bakery section. I'm not that excited about their bakery. It does have a variety of items, but most don't entice me.
They have a lot of sushi, but I haven't tried it, as I am generally suspicious of the quality of fish used in grocery store sushi. The prices here are mostly very reasonable (the seaweed salad seems a bit expensive compared to that at Nijaya, and I doubt it tastes much different).
The store is spacious, not overly crowded, and also sells plenty of plates, bowls, and cooking implements. You can also get a variety of American items here, like boxed cake mixes and soda. The parking lot is a bit of a crowded mess--look for the out-of-the-way spots around back, and avoid peak shopping times.
Also, if you eat meat and like Vietnamese food, be sure to check out Pho So 1 next door. I hear it's one of the best Vietnamese places outside of Little Saigon, although when I ate there, I was mostly thinking about how my egg rolls had pork in them (I was a vegetarian at the time, and not a single vegetarian item graced the menu) and about how some rude male diners were photographing me and my female friend with a cell phone and passing it around like we were a freak show act at the circus (this included showing our server, who didn't stop them, so I'll never go back). Hopefully this was an isolated incident.
99 Ranch Market
6450 Sepulveda Blvd (near Victory)
Van Nuys, CA
99 Ranch Website