First things first:
It is very possible to learn Japanese on your own using mostly online resources. The majority of resources you will need are available for free, you'll just want to get a few (really few) books. Moreover, you would be more successful learning Japanese on your own rather than in a class.
If you work on it almost daily, you may be able to read raw manga of almost any complexity (even without furigana) within one year. If you work extra hard, even less. And that's considering that Japanese, of all the languages I'm aware of, is the most difficult one when it comes to reading.
All of the above is true provided you approach learning the language rationally, utilizing all available resources that make your task easier.
I would say the main purpose of this topic would be to point learners to such resources, to explain to absolute beginners where to start, and to encourage those who feel they're stuck. Basically, advice from people who have already been where you might be now.
I might have a few things to say later on about a) what to learn first; b) how to memorize and retain vocab painlessly; c) how to learn big scary kanji and not lose your sanity in the process.
So please post your questions, comments, opinions right here.
And also, mina-san, ganbare!