There are multiple profile scripts that can be created according to which hosts and how many users you wish the profile to apply to. The PowerShell 2.0 help has an about_profiles goes into details. The short version (from the docs) is:
Description Path
----------- ----
Current User, Current Host $Home\[My ]Documents\WindowsPowerShell\Profile.ps1
Current User, All Hosts $Home\[My ]Documents\Profile.ps1
All Users, Current Host $PsHome\Microsoft.PowerShell_profile.ps1
All Users, All Hosts $PsHome\Profile.ps1
Name Description
----------- -----------
$Profile Current User,Current Host
$Profile.CurrentUserCurrentHost Current User,Current Host
$Profile.CurrentUserAllHosts Current User,All Hosts
$Profile.AllUsersCurrentHost All Users, Current Host
$Profile.AllUsersAllHosts All Users, All Hosts