If you're hoping to really learn the language and not just be ready for a trip with phrases, etc, your best bet is to buy 501 Spanish verbs and a secondhand textbook and give it your all. ¡Que tengas suerte!

but.

It's junk, it's outdated and no good.

Rosetta Stone is an excellent program, despite what the other answerer said. It's pricey, so if you cant afford all 5 levels just get the first 3:

Alternatively try:

If you are really on a budget, the best program I could recommend is:

It's just under $100. I've personally used that (along with Rosetta Stone) a year ago so that I could learn Spanish before I traveled to Spain and Mexico. It's the best program out there. Oh, and ignore all the silly marketing stuff on the page, they need to change it, but despite that it's an excellent program.

My college uses another software called TeLL me More, by Auralog. I found it more complete and less repetitive. It covers not only the basics, but also intermediate or advanced level. My goal was to become fluent so it was perfect for me. It has a lot of different activities: picture/word association, videos, dialogues,…, includes also grammar and conjugation. Their speech recognition is great so you can have a dialogue with the computer. You can check out their website at for a free demo or they can send you one. I found that site of reviews as well

The best way to learn a language would be through immersion, visiting these countries. Learning a language will require some time. In addition to software, you can have books which are useful as well. Audio CDs like Pimsleur for instance might help you out but you cannot get any feedback on your pronunciation so I did not like it so much.