Profile settings let you control your how other members of the site see you, and to manage your site settings.
Go to Account and Profile - Account - Account Settings to access your profile settings. Currently, the only editable setting is your profile name.
Some settings are implicitly saved and not shown there - for example, how many notes or tasks you see per page in the list views is saved as a user preference when you select a value in the respective table, but is not shown in the settings form.
More settings (notification options, dashboard views, mailing list subscriptions etc.) will be added over time.