I'm looking for coding exercises that have solutions. I've checked out topcoder and codekata but neither seem to have user posted solutions (maybe I just can't find them?).
Basically I can (try) to figure out how I would solve a problem but what I want is to learn and expand my knowledge by see how other (better) coders would solve the same thing.
ProjectEuler has some good fairly good problems that lend themselves easily to a coded solution. There is no site supported help system, but simple google searches with the number of the problem you are working on normally has good results.
Once you solve the problem, you then have access to the site solution and a forum posting that shows other users' solutions so you can learn from them, (If you solve it first).
In TopCoder you can find the solutions in Competitions > Algorithms > Statistics > Match Archive, there you select a match and statistics will be displayed. After that by clicking "[*]" at the left side of the handle name, you will be lead to the solutions submitted by that coder.