Studying for the HSK has really helped me out, and I plan on passing a new level of the exam every year (yes, up to 6). Still, I have been throwing money and time and studying Chinese while living in China, both things that will be in far shorter supply when I move back to the US. How do you guys do it (Ideally someone who has a full-time job can fill me in on the secret). I do not want to lose what tiny amount of language I have learned!

Ideally you should have a way to practice the skills that are important to you every day. That is, if speaking is important, find a way to speak Chinese with natives (maybe through Skype or QQ). Skritter will help you maintain and build on your character knowledge.

I don't think time is actually that much of an issue unless you are working two jobs or have a kid to take care of. We're talking about an hour or so per day. It's just a matter of priorities.

You could try getting a job that doesn't require work. I work at an alternative high school where the mode of instruction is via computers. If I wanted to I could play Skritter for hours a day and get paid for it.

In addition to jw1066's suggestions:
There are lots of ways to fill your free time with language learning. Some people find the writing on www.alljapaneseallthetime.com annoying, but there's a lot of good information there.

Speak. Aside from looking for every chance to practice speaking with other partners, try reciting material to your self. Record your voice. Even if it's not perfect, repetition will help increase muscle familiarity.

Read. Start with children's books, work your way up to low-class novels. You can order chinese books online from amazon.cn, dangdang.com or other retailers. Ask friends for recommendations. This is one of the best ways you can improve your understanding of the language. Change your phone and computer system to Chinese. Try reading Chinese forums. Don't use English for anything you can use Chinese for.

Watch. Watch TV series online on websites like youku and sohu.com (and many others as well; search baidu video). Chinese tv has improved over the years, and there's a wide variety of movies and television series (don't discount talk shows and other programs) to choose from.

Listen. This is the best way to fill in those chunks of time where are idly preoccupied. Driving in your car, walking down the street, brushing your teeth - any moment you can find, put on earbuds and listen. Chinesepod.com is a great choice for beginner/intermediate. BBC.com has a chinese-language news podcast. You can find books on tape (有声读物）as well. Music is really key, it can be hard to find stuff you like but it is very helpful if you do. Mentally we tend to process words learned through singing differently, which some find helps with memorization.

Write. lang-8.com has a mutual exchange system, review English material for non-native English speakers, have Chinese speakers review your writing. Short of having a friend or teacher review your work for you this is probably your best option. Do write, it is a skill that needs to be practiced to improved. Doesn't matter if it's not perfect.

Try to maximize time. Fill in those cracks. When you do this on a daily basis, it adds up a lot. Years are absolutely meaningless when it comes to language; there are plenty of people who have "studied" Chinese for 10+ years and still can barely carry on a conversation. Hours are everything.

Most importantly, have fun. Don't do something if it bores you. There are lots of ways to practice Chinese, so find things that interests you. You will do a lot more reading if you read books that you find interesting personally. Just remember that anything you do - even watching a cartoon or navigating a webpage - is developing your Chinese skills.

Although i agree with most of what digilypse has said, i wouldn't really recommend getting children's books to read. At least the ones i've got have either been so simple as to be worthless, or use language and characters which are never really used in day-to-day life.

Getting a movie and having the subtitles on in Simplified Chinese i've found to be much more productive.

There are many books written for children around elementary and middle school which are written in normal yet simplified language and are intended to give younger children a head start in reading literature.

If you're not a total beginner but not feeling up to starting a novel just yet, these are a good place to start.

Of course, movies can be a great way to practice reading as well.

I think it's OK to focus on one area only, main thing is not to do nothing when you get back from China (like I did for the last 2 years before 2010). As you move through the stages, new ways of learning come up. Skritter in 2010 has done the trick for me - however my speaking has been getting worse, but after a week in China I'm back in action.

I would go for the Chinese Breeze series or similar books written for adults learning Chinese if you can't pick up a novel yet. Pick them up in China before you take off or you're likely to pay heavy import duties.