hitting for a lot and a lot of categorized keywords - directory solution

Hi,
i've got my main raffic keywords (2 phrazes), but also loads of small/low competition keyword bringing not so much traffic (like 0,5k / 1000 a month).

loads means about 40/50 (ok, maybee not such big loads). I dont want to put them as posts because these are reserved for big traffic keywords. After something i went up with idea of putting them all in articles directory structure. for all of them i'd find the unique description for about 500-1000 words.

any free ideas or experience with this kind of structure ?