I believe I sent this by email as well, but here is the complete list of merge codes for email invites.. the first part is within the email invite, the second part is the code when within the SURVEY:
In the Invitation system:
[%%Email Address%%]
[%%First Name%%]
[%%Last Name%%]
[%%Organization%%]
[%%First Name Encoded%%]
[%%Last Name Encoded%%]
[%%Organization Encoded%%]
[%%Home Phone%%]
[%%Street Address%%]
[%%Street Address2%%]
[%%City%%]
[%%State%%]
[%%Postal%%]
[%%Country%%]
[%%Custom1%%]
[%%Custom2%%]
[%%Custom3%%]
[%%Custom4%%]
[%%Custom5%%]
[%%Survey Link%%]
[%%Secure Survey Link%%] (Enterprise only.)
[%%UnSub Link%%]
[%%TrackingCode%%]
In the Survey:
[%%Invite_FirstName%%]
[%%Invite_LastName%%]
[%%Invite_EmailAddress%%]
[%%Invite_Organization%%]
[%%Invite_Department%%]
[%%Invite_HomePhone%%]
[%%Invite_FaxPhone%%]
[%%Invite_BusinessPhone%%]
[%%Invite_MailingAddress%%]
[%%Invite_MailingAddressCity%%]
[%%Invite_MailingAddressState%%]
[%%Invite_MailingAddressPostal%%]
[%%Invite_MailingAddressCountry%%]
[%%Invite_Title%%]
[%%Invite_URL%%]
[%%Invite_Custom1%%]
[%%Invite_Custom2%%]
[%%Invite_Custom3%%]
[%%Invite_Custom4%%]
[%%Invite_Custom5%%]