We do class names, family names, and line names. Each class gets a name based on their letter. (We're officially the Luscious Lambdas, but our mom always likes to call us the Lambda Lesbians...)
Then family names, these are made up by whoever's first in the family, so since we're small, probably a Charter. They can be really fancy or simple, it's up to whoever does it, but generally they're some kind of commentary on the member and their line, what they're like and all.
Then line names, which are suggested by everyone and decided by your big, given out at some point during pledge (ours were given out at the end, but our sisters at another school nearby got theirs right away) and then you find out what your nickname means at the end.
Mine's Cherry Blossom.

I think more often than not, they don't really get used, although they are usually used when someone's putting your name on a present, or when people are being cutesy and writing on each other's Facebook. :P