Several.
Among other things, in Races of Eberron, there's substitution levels for Changeling Transmuters and Changeling Egoists. You could even make the case for a Changeling Telepath, given their ancestors are a race with Detect Thoughts. Changelings have an affinity for this.
How about a changeling who creates (or follows) a fighting style built around morphing the body mid-fight? Lengthening limbs, growing increasingly thin or short to dodge blows, etc. I'd allow a player (or as a player, if my DM would allow) create feats for a monk to develop those feats.
But the way I see it, it's also less about just disguise and infiltration as it is defense mechanism. Imagine two muggers follow someone into an alley. The someone, a changeling, knows he's going to get attacked - so he changes his appearance - before their eyes - into a vampire. These thugs may know about changelings, but are they going to take the risk that he isn't an undead monster about to eat their face?
With proper planning, you can have some really nice psychological tricks up your sleeve.