Blake's 7 was a British sci-fi show from the 70's and 80's, which centered around Roj Blake and the crew of the renegade starhip Liberator. Blake had been a leader in a now-failed rebellion against a tyrannical government, and now traveled through space with a rag-tag bunch of misfits as his crew - one of whom is a psychic - on the run from the government, and trying to help the downtrodden. That's half of Firefly right there.
Outlaw Star was a science fantasy anime from the 90's that debuted in the U.S. in 2001. It centered around the crew of the titular starship, the Outlaw Star. The crew of the ship would fly around human-controlled space (which, culturally, was basically "The Old West meets China"), taking jobs from whoever was willing to pay them. Oh, and one key member of the crew is a mysterious teenage girl who arrived naked in a box (in the fetal position, even), and who everyone in the galaxy is trying to get their hands on, because in her brain, there's some deep secret that'll completely disrupt the status quo. That's the other half of Firefly right there.