I have been learning Spanish since a month now. (Me encanta aprender espanol!)
I know, that probably doesn't make me any expert to write an article as this. But I believe you will find some worthy recommendations here (specially resources you should use). Best of all they are all FREE!
Learning through mems
Earlier in the year when I read Joshua Foer's Moonwalking with Einstein I was fascinated with this whole business about remembering things. Certainly, the memory championships are won by ordinary human beings and not wizards. So it was exciting to learn a technique or two about improving memory. Cutting short, there was a Guardian article on how Joshua Foer learnt a language in 22 hours. There he refers to a site built by former memory champions called memrise.com. A site where you can learn languages (among other things) through visual cues (mnemonics or what they shortly call as "mems"). Till date, I remember some of the complicated phrases in Spanish thanks to memrise. It is fun and addictive. Give it a shot!
Learning via apps
One of the best language learning apps out there is Duolingo (only available in iPhone as of now). Thanks to Mr. Ashton Kutcher, who tweeted this and there hasn't been a day where I didn't use this app to learn Spanish. Ok, there was a day and the Duolingo team promptly sent me a reminder (whoa!) that daily practice is essential to learn a language. So now you must wonder, there are several apps, so why this app? I think what works in this app is you can take short lessons in under 5 mins or so (if you were waiting in a line somewhere, commuting, or just bored), you could switch to this app and learn a word or two. Also, the app structures the lessons really well (so you are progressing from one level to another) and is very comprehensive!
Learning via podcasts
I love my iTunes! Specially podcasts and iTunes U. I could sit on them the whole day and forget to work. They are that addictive. One of the most popular language learning series on iTunes is Coffee Break Spanish. These are short podcasts (weekly I think) that cover Spanish lessons offered by Scottish anchors Mark and Cara. They make it really interesting through conversations, basic phrases, holiday jingles and what not. Basically very very simple but effective.
Learning via iTunes U
And then there is the traditional way of signing up for a language course. This is the least recommended, honestly. Because you are going to find yourself less and less motivated to stick to it. But one of the things I was struggling with while learning Spanish is grammar. Grammar, yes, is important. So I found a course by University of Arkansas on iTunes U called the 5 minute Spanish. This focuses only on grammar and is a 5 minute series (again!). Very effective in getting rid of those grammar questions.
A nagging question for instance was when to use "es" and when to use "esta" in Spanish. A 5 minute lesson in this course just crushed it!
Learning with a buddy
Honestly, if I continued to live in the States, I would easily find a Spanish speaking buddy. And that is probably the best thing to do anyway - practice speaking a language with a native speaker. But since I am in India, I learn by practicing with a friend who is also interested in learning the language. So we try to do conversations as if we were two native Spanish speakers. It is fun to make mistakes and laugh over it. Plus, we add our own creative ways of remembering it :)
Learning by listening/reading
This is something I caught on to a little late because I had to build up to the basic Spanish words before I start watching Spanish videos. I picked up a Spanish book recently and I watch Spanish commercials on YouTube. Although, I am still on the lookout for a nice Spanish soap or TV show that I can follow (Recommendations welcome:))
So really when I was watching Life of Pi I jumped up at the scene where Pi is in the hospital and there is a headline in the local Mexican newspaper that reads something like "Chico 277 dias..."
I immediately grip my friend's arm and say hey I know what that means. I had to show off you know ;)