I like making my own blue cheese and use a recipe from Suzanne Somers:

Roquefort Dressing

1 Tbs red wine vinegar 
4 oz crumbled blue cheese, preferably Roquefort 
3/4 cup sour cream 
Salt and fresh ground black pepper

Combine the ingredients in a food processor and blend until well mixed (or you can use a whisk in a bowl). It's a thick dressing , you can add a bit more vinegar if you wish to thin it out.