$50 an 1/8th is pretty standard for high end strains like white widow, northern lights, etc. but usually comes down to $300-$350 for an oz.

There are hundreds of strains out there that are really good and new ones pop up all the time. I'd be a bit wary of looking for any particluar strain though. Being able to get any drug and having access to any one particluar strain of weed out of hundreds are two different things. Chances are if you specifically ask for something like White Widow the guy you get it from will most likely get a bag of some decent bud that he has no idea what it is and call it white widow to make you happy. My personal feeling is that, unless you're getting it from a medical mj source, the grower, or someone real close to the grower, the chances you're really getting the strain that the dealer claims it is are pretty slim.

Anyhow, more important that what the bud is named is how stoned it gets you. If it doesn't have any seeds, is nice and green with lots of cystals all over it, you can smell it across the room, and one bong hit gets you stoned-who gives a shit what strain it is.

In any case here is a great link with descriptions of a couple of hundred strains

http://www.smokersguide.com/sg/index.html