Plant Borage to deter tomato and cabbage worms, it will also improve the general health of the soil in your garden. (it's cool, blue star shaped flowers that are edible, seeds out really well from year to year, I bought my seeds for it off ebay a few years ago)
Geramium also repels cabbage worms , and aphids.
Thyme deters cabbage worms (I love the smell of thyme) (thyme is really easy to clone, I just whack some off, get the ends wet, dip it in some quick root powder and plant it, grows like a charm every time)
Yarrow increases the oil content in herbs and attracts ladybugs, (ladybugs eat ahpids) (yarrow spreads easily and grows wild a lot of places)
Tarragon repels most pests.
Most of these will also create scents to mask the smell of your special herbs.