Here are some links that might help:

http://msdn.microsoft.com/en-us/library/ms190030%28v=sql.105%29.aspx

SEND queue, REDO queue from performance counters:

http://www.mssqltips.com/sqlservertip/2228/sql-server-database-mirroring-performance-monitoring/[/url]

http://sqltwist.com/archives/179