Depending on the language you want to learn, it is very possible to learn it for free online. But with a few dollars invested, you can make learning a LOT easier.
Most minimalists will concede that you need at least two items: A dictionary, and a grammar or phrase book. A concise dictionary is better, because you can take it with you where you go, and you'll have a higher chance of using it, even though you may not find EVERY word. I have one for Persian which has 8,400 total entries. You can be conversational with 2,000 (if you pick the right ones). A phrase book is good for getting you a few basic phrases to at least start speaking instantly and build your confidence and ability to at least open a conversation with a native speaker. Both of these are in free, less comprehensive online versions, though. So depending on the cost, it might be worth it to you to pick them up, or just keep a computer handy for all your questions.
A rising trend seems to be the abandonment of traditional grammar study. You don't need to know what a particle is, or how to conjugate a verb to past perfect or past continuous, or why. Rosetta Stone makes use of this "organic/natural" method of learning a language, to large success (though their success is mainly due to the verbal feedback via voice recognition). Mr. Kaufmann's website "LingQ" also uses this approach that all you need to do is build some vocabulary, and the grammar will come naturally as you immerse yourself in the sound of the language being spoken.
Also depending on the language you want to learn, there are online resources. The Internet is full of free language learning information, some of which is put out by nations and governments to further spread their culture and language. I think it's a great idea, and it certainly works for learning the basics before going somewhere. There's a reason Google is fast becoming a verb. ;-)
There are online translation and dictionaries to use. I know for Persian, you can install the font via the Microsoft website, and look up Persian words at http://www.farsidic.com or other sites. Another place is myhappyplanet.com, and other sites of the same type; sites that you can go to and find online communities of other learners of the language, and language partners who speak as their first language.
Another thing that repeatedly comes up in my attempts and searches is the music and TV of the language. You may not understand what is being said, but you begin to pick up the rhythm and tones of the language. Babies do this with their first language, and even on the day of their birth, prefer the rhythm of their mothers' language over others (and can distinguish between the two, unless they are similar languages), even though they are far from conversational. The more you hear it, the more it becomes natural to you, and you also pick up the sentence structure, so when you do actually learn something, you can tell if it's "supposed to" sound that way. For Persian/Farsi, I use http://www.bia2.com for (Iranian) music, and NoorTV for the Afghan Dialect (Dari) being spoken. BBC has Pashto and Farsi (BBCPashto.com and BBCFarsi.com) for live reports and written news stories.
So some methods I've found helpful:
Get a dictionary and a phrasebook/grammar book
Online free language teaching sites (Google it!)
Online communities with language partners
Online music and media (TV, radio etc.) sources
If that all seems like too much work for you, maybe you should just find the resolve in your pocketbook and buy a complete program or go to a class. It's all user dependent.