Great pic TDevil...Curt has a nice pic of dinos, too. Here is a great article I found on bubble algaes...nice pics, too:
Bubble Algae
One method I remember reading of getting rid of a small cluster was from ReefLady....cover the colony up with an empty clam shell, depriving them of light. Of course there are emerald crabs, but I'm not so sure they work all that well. Lastly, if you can take the rock out, you can use tweezers to pull the algae off with tweezers at its base.