While not primarily intended for this use, I've used EasyHost for these kinds of things with good results.
You could also use a combination of Apache Authentication and a filemanager program (I like ffileman) to provide each user their own "space", while retaining ownership (meaning all files remain "owned" by your *nix user). If you didn't want them to have that much capability, you could do the same thing and use a simple upload manager instead of a full filemanager.
Another approach would be just to make a separate DH user for each client, and actually give them their own space on DH under your account.
That has certain risks associated with it (they'll have "full access" to that web space without any of the controls you could implement with the previously suggested solutions), and now you will have a little potential inconvenience in dealing with files they upload (the files will be owned by their user, not yours, etc.).
There are other solutions too, depending upon what you envision them being able to do (groupware scripts with file repositories, etc.). It really just depends upon what you want to do, how capable you are working with scripts/programming, and what degree of access you want them to have.