DH loves food, so I would automatically go that route. Maybe surprise him with his favorite breakfast one morning, then sneak his favorite candy bar into his lunch (assuming he takes a lunch to work). Does he have a favorite movie, maybe buy it for him (if he doesn't already have it) and watch it one night after Zack goes to bed. DH also loves beer, so if I had his favorite cold beer waiting for him when he got home from work he would be in heaven. Something easy would be baking his favorite cake or making his favorite dessert for his actual birthday may be a nice surprise. I told you, the way to my DH's heart is definitely through his stomach!

We do not have extra spending money, so I have become the queen of gifts that aren't really gifts. It's more like thoughtful things that you can do that maybe only you know about your BF.