Processionals and Recessionals
The following are some examples of the stately marches that can be used:
Wagner - Bridal Chorus from Lohengrin (the traditional "Here Comes the Bride") 
Mendelssohn - Wedding March from A Midsummer Night's Dream (Played faster when used as a recessional, and more stately when used as the bride's processional)
Bochsa - The Bridal Ring
March Napolitaine
Gounod - March Pontifical
Purcell/Clarke - Trumpet Voluntary (also commonly used as either a processional or recessional)
Purcell - Trumpet Tune
Handel - Largo from Xerxes
Hornpipe from Water Music
Air from Water Music
Beethoven - Ode to Joy
Bach - Wachet Auf
Sinfonia from the Wedding Cantata No. 196
Sheep May Safely Graze
Grandjany - Aria in Classic Style
Less common examples of beautiful music that can be used for a wedding processional include:
Mascagni - Intermezzo from Cavalleria Rusticana
Morricone - Gabriel's Oboe (Nella Fantasia) from "The Mission"
Vivaldi - Largo, from "Winter", The Four Seasons
Other wedding music selections:
Bach- Air on the G String
Jesu, Joy of Man's Desiring
Ave Maria
Arioso
Massenet - Meditation from Thais
Pachelbel - Canon in D
Saint-Saens - The Swan
Puccini - O Mio Babbino Caro
All I Ask of You
Dirait On
What A Wonderful World