The most important thing is actually integrating Japanese into your everyday life.
For this, I think Twitter is a really good option. Ever since I started following Japanese people, my Japanese has improved significantly. You pretty much cover all bases at once: grammar, how natives converse, vocab, idioms, etc. This combined with Rikaikun (if you don't know what it is, Google it and get it ASAP
) makes the process really nice and enjoyable.
It obviously depends on who you follow. I generally follow Japanese game developers and Street Fighter players so I tend to get topics on those, but they also post alot of random news, good places to eat, etc.
Lang8 and Youtube are also really good; You've got Lang8
But for others who don't, I really recommend it. In a nutshell, you create a blog and natives come and correct it for you, give you more natural options for what you wrote, etc. It's really, really good. Problem is finding a topic to blab on about, haha. YouTube pretty much covers all the speaking side of things.
I always used to worry about vocab, but really, you more you read/listen to Japanese, the more you pick up. What I do now is that everytime I hear I word I don't know the meaning of, I'll check it up on NihongoDict, Denshi Jisho and then make a mental note of it. I used to write it down in a little notepad but I never checked it though I might start doing that again since I'm starting to forget some, haha. Whatever works best. =]
It's kinda funny, one of my friends got a really high level of Japanese without picking up a single textbook. I can kinda see how now.
Random: 今日は不毛すぎたなー