I've just started playing around with it, and didn't see one mentioned in the tutorial, and grepping everything in the arc0 directory didn't turn up anything promising.
In Arc you would just use a list, I believe. What type of things would you like to do with a vector? If you give some code examples I'm sure someone will translate into Arc.
Vectors are very useful when accessing random positions in array. Lists are very inefficient for this because they need O(n) operations to access one item, whereas vectors only O(1).
