Unique Elements in a List

[superprad at gmail.com]

Is there an easy way to grab the Unique elements from a list?
For Example:
data = [0.1,0.5,0.6,0.4,0.1,0.5,0.6,0.9]

what I am looking for is the unique elements 0.4 and 0.9 with their
index from the list.
Probably something like a Hash Table approach!!
I would like to get this done without unnecessary overhead.And the list
could be essentially anything strings,floats,int etc...

Or is it already avaliable as an attr to a list or an array?
I dont remember seeing anything like that.