*Show up to work one day (with kids in tow if you have young ones at home), and deliver a favorite snack or drink to him. You could also include a sweet card, balloons, drawing from the kids, or anything else that would make him smile.
*If he has a private voicemail box at work (make SURE it's private!) you can call when you know he's on lunch break, and leave him a wonderfully suggestive message.
*Sneak by his work parking lot and decorate his car. Even better if you have a copy of his key! Write on the outside (maybe your initals inside a heart?), put balloons on the inside, leave a note on his seat, whatever! Have fun with it -think creatively just like people do with "just married" cars.
*Slip a love note and favorite candybar into his lunch if he packs one.
*Kidnap him one lunch break and to save time, you could bring lunch with you. Picnic in your car, at a park, or in his break room.
*For a whole week, why not make it a point to let him know how much you appreciate how hard he works and how faithful he is to his job at least once everyday. You could choose a different aspect each time: how he is always on time, how he has such high standards of excellence, how he perseveres through the tough times, how he manages to hold up under the preassure of deadlines, etc...
Nothing says "I love you" to a man more than showing him respect in his professional life. You just might be surprised by his response!