We all know arrays are indexed collections. We also know that keys in array are integers and that the indices start at zero. So lets jump into some examples:
a= ['The','Dark','Side','Of'.'The','Moon']
a painful way to create the array 
.another way
a = Array.new
a << "The"
a << "Dark"
a << "Side"
a << "Of"
a << "The"
a << "Moon"
same can be achieved by
a = %w{ The Dark Side Of The Moon}
much easier eh.. 
that can also be achieved by
a = "The Dark Side Of The Moon".split(" ")
awesome :)
Here is a list of some useful array functions:
To remove all elements from an array use the “clear” method.
a.clear -> [ ] #an empty array
To find out the length of the array use “length” method. Returns an integer
a.length -> [a,b,c ] #length array
To remove the last element in the array use the “pop” method. Returns an object or nil
a = [ "a", "m", "z" ]
a.pop -> "z"
a -> ["a", "m"]
To add an element(s) into the array use the “push” method.
a = [ "a", "b", "c" ]
a.push("d", "e", "f") -> ["a", "b", "c", "d", "e", "f"]
As with any collection in ruby, you can use the “each” method to loop through its contents. It call the block once for each element. The element will be passed as a parameter.
a = [ "a", "b", "c" ]
a.each {|x| print x, " - " }
produces:
a - b - c -
To loop through an array using the index use the “each_index” method.
eachindex arr.eachindex {| anIndex | block } -> arr
a = [ "a", "b", "c" ]
a.each_index {|x| print x, " - " }
produces:
0 - 1 - 2 -
To find out if the array is empty or not use the “empty?” method. This method returns either true or false
arr.empty? -> true or false
To join the elements of an array into a string use the “join” method. An optional string separater is present as a parameter.
[ "a", "b", "c" ].join -> "abc"
[ "a", "b", "c" ].join("-") -> "a-b-c"
To concatenate array you can use the “concat” method.
[ "a", "b" ].concat( ["c", "d"] ) -> ["a", "b", "c", "d"]
To remove the nil elements in the array use the “compact” method.
[ "a", nil, "b", nil, "c", nil ].compact -> ["a", "b", "c"]