when you log in as the "new" user, do you have Administrative rights on the machine?
If so, it may be possible to go back to the Users folder and change the name back again. Don't hold your breath though.
If you actually created a whole new account, then you will find that there are similar files in your new account. ALL accounts have similar files in them. Music, Pictures, Movies, Applications, etc.
Using an account with Administrative rights, you may be able to move stuff from the Documents folder, Music, Pictures, Library/mail, Library/Application Support/Addressbook, Library/iTunes
If you are not successful in getting your old account working, a program like Disk Warrior will rebuilt the directories and allow you to move stuff to an external drive for later inclusion into the new account.

Good luck.