Something that I have found to keep the spark alive for us is just simple things like catching his eye across the room, and then sharing a special smile that is just for him. When I write it out it sounds kind of dumb but I have found it something that makes him realize that even if we are with a crowd of people or if we are doing our own thing (working on separate projects) I can still be thinking about him.
I think eye contact and facial expressions can communicate a lot and I encourage you to make sure you pay attention to your husband, that you give him eye contact so that you can communicate your love and respect to him in that way.
Now don't start staring at him in someway that he will think you have lost your marbles but rather in a way that makes him realize that you think he is hot or just that you are thinking about him.
I hope that make sense..... :-)