With H*Sphere you can create several accounts under one login and easily switch between them after you log into the control panel.

Account Info menu has two items for multiple account management: Choose Account and Add Account:

To switch between accounts, select Choose Account in the Account Info menu. You will be taken to the page listing all your plans:

Click the Select icon for the account you would like to enter.

To create a new account, click Add Account in the Account Info menu. You will be taken to the page listing all the evailable plans:

Click the Select icon for one of the listed plans.
This will begin the account creation wizard, which is identical to that in the signup procedure.