Let me make one thing clear--the acquittal of George Zimmerman was a travesty. Granted, it was dwarfed by the larger travesty of how long it took for there to be an arrest, but it was a travesty nonetheless. That being said, it's way, way, way too premature to call for federal civil rights or hate crimes charges against Zimmerman.
No matter what the jury says, the death of Trayvon Martin was a criminal act. However, there's too much we still don't know about Zimmerman's state of mind that night. As was mentioned on today's Morning Edition, you'd have to prove Zimmerman was motivated by racial hatred. From my non-lawyer's perspective, to charge Zimmerman with violating Trayvon's civil rights, you'd have to prove that he was so fed up with black "assholes" and "punks" traipsing through his neighborhood that he set out to confront the next one--and Trayvon happened to be that next one.
That being said, though, I suspect the prospect of federal charges may be why Zimmerman's lawyers are falling all over themselves to get their client immunized from any civil suits. As we all know, the Fifth Amendment's protections against self-incrimination aren't nearly as strong in civil cases as they are in federal cases. Which means Zimmerman will almost certainly have to testify. And you can bet your bippy that he'll get torn to shreds over the numerous inconsistencies in his story. Trayvon's family would also have much more latitude to conduct searches and subpoenas.
In all likelihood, a civil wrongful death suit is the only way at this point to make Zimmerman answer for Trayvon's death. But if the DOJ is ballsy enough to do it, they could use any evidence gleaned from a civil suit to rack Zimmerman up federally.