Yes, there is a way by which you can classify or group your sites according to clients or similar themes. This is especially useful if you have many sites in your account as it makes for easier sorting.
For example, you could have a group 'Personal Websites' for your own sites and a group 'Client A', 'Client B' or 'Client C' for your clients' sites. If you have added several websites with different themes, you could classify them accordingly by grouping the e-commerce related sites under 'Shopping', health related sites under 'Health' and so on.
In order to group your sites:
To add a new site, click on 'Grouping Options' on the top right hand corner of the 'Add a Site' page
Click on 'Create New Group' from the drop down box under the Site Group section
Enter a group name and click on 'Save Group'
The site that you add will be saved under this group.
In order to manage or edit already existing sites in your account:
Click on 'Edit a Site' in your account
Click on the site you wish to edit
To save the site under an existing group, choose the same from the drop down box under the Site Group section
To create a new group, click on 'Create New Group' from the drop down box