Is it possible to change the time increments in the Date/Time field? We have a date/time field shown to render the time for a series of workshops but right now Craft only increments in 30 minutes.

Is there a way for us to render 15 minute increments?
Not currently, but it should probably be a setting on the field.

Craft currently uses jquery.timepicker (in craft/app/resources/lib/jquery.timepicker/jquery.timepicker.js) and is just going with it's default step: 30.

I'll add it to “The List”™.