I see two problems here: Getting new users to help other users, as in helping them learn how to use the site, and getting new users to participate in Q&A.
Getting New Users To Help Other Users:
The reason new users don't help other new users is because they don't yet understand the norms of the community. A few days ago, a user with a little over 2000 reputation on Stack Overflow commented on a 500 rep users answer saying that he would upvote, but he wasn't going to because there was an error in the code. So I replied:
If you know the error, consider fixing with an  on the user's behalf. You do have full editing privileges after all. ;) This isn't a contest, we can (and should) all help to create great answers! This also demonstrates to new users how editing -- which is at the heart of SE -- can turn so-so answers into great ones. Good luck!
In response to Yawus, I do believe that downvotes must be used. If content is poor, and you cannot fix it, it needs to be downvoted. No good will come out of letting poor content fester in with the 0 voted posts, or worse, rise to the top due to a sympathy upvote. New users learn much faster when poor content is downvoted, and other users see this as well. Remember, they're new users to Stack Overflow, not new to the Internet and life in general. This doesn't mean they can't write good content if they try, and the sooner they learn, the less painful it will be for everyone involved.
Just imagine being the first moderator or 10K user to delete or downvote a user's comment as an answer, who had been doing this for a week because people didn't want to downvote. Now, instead of learning something, the user just thinks the moderator or 10K user is a pompous jerk. The new user continues posting poor content, because bad habits are hard to break, and now other new users have seen this poor content too, and they think it's okay too. Remember, this isn't to say you can't reverse the downvote later if the person fixes the problem. I strongly encourage this. ;)
Getting new users to participate in Q&A:
The answer to this is, you can't. People are going to participate when they feel like participating. Some of us were just Googlers until something happened that induced us to create an account and write an answer. Some people prefer to simply read, and that's fine.
Also, I'm not really sure this is a problem, as your thinking about reputation is a little flawed:
c'mon guys with rep less than 1000 you know this one!
Knowledge has nothing to do with reputation. There was a guy on meta earlier who asked a question about answer quality. He didn't even have 100 reputation, and he was already writing some really good quality answers on Stack Overflow. The guy was an experienced programmer who recently joined Stack Overflow. Yes! Believe it or not, there are expert programmers out there in the world who don't have a Stack Overflow account yet.
The fact is, new users participate all the time. The ones that participate a lot eventually gain reputation. Therefore, when you look at a random question from a year ago, and you see nothing but high rep users, consider that, when that person answered the question, that person didn't have the reputation that is listed on the answer today.
In other words, if you look at some of my answers from early January 2011, I had less than 500 reputation back then. Today, it shows 11.6K. In other words, unless you actually calculated my rep on January 2nd, 2011, you wouldn't know that I was a new user then.
What I'm trying to imply is that our minds are sort of tricked into thinking new users aren't participating when they are, they're just gaining reputation, so their older answers no longer say "52 reputation"
In summary, without some hard data, I'm not really convinced there is a problem with new users not participating in the Q&A part of the site; however, with gentle guidance from existing users, new users do learn to help others learn how to use the site.