Exchange 2007 Perfmon Counter Guidance
Technet web now has an Exchange 2007 performance counter guidelines in-case your not going to monitor Exchange 2007 with System Center Operations Manager. The performance counter information is divided into sections based on the Exchange Server roles. This information will be an excellent resource to Operations Manager Admins helping support Exchange 2007 implementations.
http://technet.microsoft.com/en-us/library/bb201720(EXCHG.80).aspx