SPOILERS


Cloud Strife - not much to say here
Barret Wallace - original name was Bullet, which is self explanitory
Aerith Gainsborough - can be rearranged to spell 'I, earth'. Gainsborough is a small town in Lincolnshire.
Tifa Lockheart - possibly derived from 'Tiphereth', one of the ten sephirots that represented glory and beauty.
Red XIII, aka Nanaki - Nanaki is an anagram of Anakin (Skywalker). Another reference to Star Wars apart from Biggs and Wedge.
Cait Sith - not sure about this one
Cid Highwind - there's got to be a Cid, and this one just happens to have similar skills to Kain Highwind, and its the name of his airship.
Yuffie Kisaragi - I like the name, not sure of its meaning though
Vincent Valentine - you've covered that
Sephiroth - the sephirot are the ten attributes created by God through which he can project himself to the universe and man, much like what Sephiroth was doing from inside the Northern Crater. Good choice of name.