The grammar conjunc.grm deals with coordinate and subordinate conjunctions.  At present it includes a few nodes that classify common words which are used as conjunctions.  It also recognizes a comma, or a conjunction optionally preceded by a comma, as a syntactic type COMMA-COORD or COMMA-COORD which can be used to separate words and phrases of the same syntactic type in lists like "big, bold and brassy", "the first two, the next two, and the last three", "fish, soup, or salad", and "a good number or just a few, but not none".