You can create (aka import) email contacts in Exchange 2007 from the command line using PowerShell (the Exchange Console). The PS script will read the contact information from a CSV file.

Here is the powershell (Exchange Console) script/command:

Import-Csv contacts.csv | ForEach { New-MailContact -Name $_.displayName -ExternalEmailAddress $_.Emailaddress -OrganizationalUnit "domain.com/company/email/contacts" }
NOTE: be sure to adjust the -OrganizationalUnit parameter in the command above.

CSV file: (contacts.csv)

displayName,Emailaddress
Mike Wood,michael@example.com
John Q. Customer,johnc@example.org
etc,etc@example.net