How can we eat healthy food and stay within our food budget?

My girlfriend talks about how expensive healthy food is when compared to junk food.  Fresh fruits and vegetables cost more.  Even at the cafeteria at work, a salad (which is charged by weight) costs more than a burger and fries.  We should consider the healthy food as an investment in our future health because it does cost more.  What are some ways to hold down the grocery bill while eating more healthy? 

Buy in season and shop for weekly specials on fresh produce.  

Find a local farmers market and comparison shop there.  

Plant some veggies and herbs in your flower bed.  I did. 

Do you have any suggestions you utilize to keep your grocery bill within budget while eating healthy?