Running a query to display only unique fields

I’m drawing a total blank on this. I’ve tried various search terms, but come up dry.

Basically what I need to do is figure out how to do a drop down menu that displays only the unique values in a certain field in a recordset (using dreamweaver cs3, asp, and an access database). IE, I want to display all the unique zip codes in the zip code field. If 33333 shows up a hundred times in the database, I only want to see it once, and every other zip code only once, no matter how many times each is in the database. Could someone point me to a tutorial on something like this? I’m sure it’s pretty straight forward, but I can’t seem to find anything, and I can’t even figure out how to approach it.

Maybe after some sleep I’ll do better, but any help would be much appreciated!