I've tried Pimsleur, which uses native Spanish speakers who are actually from SPAIN, therefore the Spanish is very different than what you would hear in Latin America where I'm interested in traveling to and living at. I've tried Michel Thomas, who's voice and accent I simply cannot stand, and I've also used FSI (Foreign Service Institute) which I personally like although it's not the best choice for a beginner as it takes 2 hours a day of practice for 6-8 months to complete, as well as a program called Learning Spanish Like Crazy (I know, they should've picked a shorter name).

Out of all of those, it's very difficult to choose one 'best' one and I actually recommend you get more than one because the 'overlap' is VERY beneficial to your learning--I started Learning Spanish Like Crazy while I was on Level 3 of Pimsleur Spanish. However, I personally found that Learning Spanish Like Crazy not only used the 'Pimsleur Method' of learning a foreign language, which I love, but it had a LOT more material in it than Pimsleur did--I felt like I was much farther along after completing level 1 of LSLC than I did after I had completed all 4 levels of Pimsleur Spanish.

Learning Spanish Like Crazy has 2 levels and each level takes approximately one month to complete, at a rate of one lesson per day (they're just the right length: 25-30 minutes each). It's available as an audio MP3 download that is entirely digital and comes with written transcripts of all dialogue in pdf format, so that you can download it immediately and start learning, or it's available on CDs that you can purchase and have mailed to you at an additional cost.

Additionally, purchase of Learning Spanish Like Crazy includes access to a private forum on the LSLC website where you can ask instructors questions about Spanish and get help from and interact with other customers who have purchased LSLC and are themselves learning Spanish, probably at about the same level or higher than you are.

The few things I don't like about LSLC are as follows: it's almost entirely audio, so you're not going to get much reading/writing practice, but it does bill itself out as a course to help you SPEAK Spanish, which is what most people are far more interested in than reading/writing, and they also include written transcripts of everything actually spoken in the lessons, so you can always feel free to use that to follow along, check a word you didn't understand, or to improve your Spanish reading skills.