Rosetta Stone is an interactive CD-ROM program that teaches you Spanish (or almost any other language) in the most natural way possible. Through a series of photos that are cleverly used in juxtaposition to convey meaning and difference, you can listen to and read the language simultaneously and later practice your writing and speaking skills (with the use of a microphone). A major advantage of this approach is that it cuts out "thinking in English" and then translating, which can slow the learning process.
If you are teaching yourself Spanish, it is essential to acquire a book that will break down the grammar and rules of the language for you. Two of the most straightforward and approachable books that you can find in this department are "Spanish for Dummies" and "The Complete Idiot's Guide to Learning Spanish." Both of these books come with a CD to help you listen to segments within the book so you can develop an ear for it. They also explain the technicalities of accents, sentence structure and grammar so that they are easily digestible.
Having a English/Spanish dictionary is crucial to expanding your vocabulary. Modern technology has made it so that you no longer have to tote around a heavy book. Companies such as Larousse have applications for the iPhone that you can download and have at the tip of your fingers wherever you go. Every time you come across a word you don't know, look it up and add it to your vocabulary list.
As your skills progress and you nail down the basics, pick up some Spanish novels and poetry to enhance your ability and comprehension. Try reading the works of classic Spanish authors, such as Pablo Neruda or Federico García Lorca. Another option is choosing a book that you love and know well in English, and getting its Spanish translation. This will make it much easier to follow along and pick up the Spanish meaning. Acquiring the corresponding audiobook and listening while you read along will help improve your accent and listening comprehension.