Try DB Cruiser Online:
 
 
  1. Click here to get to the the main screen

  2. On the main screen, select (click) "Demo Database (1) - Oracle 10g Express" or ""Demo Database (2) - MySQL". The userid and password will be filled in automatically
    Note: you must click the connection on the dropdown list to fill in the userid and password.

  3. Hiy "Enter" or "Return" key, or click "Connect" button to login.

  4. Repeat the step (2) and (3) above several times to experience multiple simultaneous connections.