Blow by Blow: DM's Guide to Combat Narrative

From the publisher:
The cry of "Initiatives!" quickens every role-player's heart... or it should.

Your scenes of epic battle should be in a John Woo movie; filled with drama, action, cut scenes, cool slow-mo effects and leave the players with a sense of accomplishment at the end.

The attached gives some advice on getting/keeping your players engaged and attentive during combat. It's in small bite-sized pieces with some optional homebrew rules scattered that could help, depending on your game style.