Here’s a vocal music extravaganza that offers the best of Boston with tickets to the area’s premiere groups, including: Handel & Haydn Society (2 tickets for a 2008-2009 season performance); Chorus pro Musica’s production of Carmen (Sunday, June 1, 2008 at Jordan Hall); Boston Camerata (a pair of 2008-2009 season tickets); and Boston Gay Men’s Chorus (2 tickets to ExtrABBAganza on June 12, 2008)