Well, here's my short list of how I avoid (and how I screw up and endure) grinding:
The last enemies standing start making different decisions. If most of the bad guys are down, the last few guys start doing something else. This may be running away, surrendering, or suicidal attacks, depending on their psychology. This changes up the fight.
When something cool happens, roll with it. I've forgotten this one too many times (and I am embarrassed to admit it). If the rogue unloads a cool daily, couples it with backstab damage, and takes the big baddy down to 1 hit point, just LIE! She killed it, OK? She's a bite-sized badass. Let her have the glory, and don't make someone else pick him off with a plink attack. Can you tell I forgot about this one recently?
Try to get the party to use their cool stuff as a group. If someone is unloading a can of whoop-ass in turn 2, suggest that others might hold off till turn 3. If everyone unloads their dailies early, the cool factor gets muted by the quantity. If one person is cool every round or so, it seems like each round is very cool.
Recharge powers. If the combat is getting less dramatic, I don't care if you didn't roll a 5 or 6. The cool power recharges, OK?
Spread out or bunch up. Don't let your villains move around in predictable ways. Cluster some together to pile on the hurt (and let the area effect attacks mop them up). Move some bad guys to one end of the room, and the others to the other end. Make the party move around to deal with them (even just one sniper on the opposite side can be cool).
I think the danger in the grind is when all you are doing is spamming at-will powers. Move around, stealth some, bull-rush somebody or grab them. Don't get in the trap of thinking that all you do in combat is unload some damage each turn. That's the real grind.