1. Foods high in omega-3 such as salmon, mackerel etc. Flaxseed is ok but not as good as fish oils.
2. Whole grains and legumes for their high fibre content. Soy/tofu is especially known to be beneficial - as is oatbran and barley bran (both which are high in both soluble and insoluble fibre).
3. You also want to eat foods high in vitamins and minerals - especially potassium, calcium, vitamin C, Vit B6 & B12 and magnesium - so lots of vegetables and fruits (especially citrus, broccoli, leafy greens etc).
4. Foods such as onions and garlic - they contain sulfur substances that help.
5. Celery is also known to help decrease BP.
Then just stay away from really salty foods, foods high in saturated fats and highly processed foods as well...