Since my parish is the Church of St. Paul the Apostle, we'll be celebrating that great conversion on the road to Damascus. The feast is particularly important during this Jubilee Year to the Apostle Paul. The jubilee is being celebrated from June, 2008, to July, 2009, in honor of the bimillennium of St. Paul's birth.
The first reading at Mass tells the conversion story.
In the Gospel, Jesus (appearing after the Resurrection) tells his apostles to go out into the world and proclaim the Gospel -- a teaching lived explicitly by St. Paul.
From the "longer ending" of Mark Chapter 16:
Jesus appeared to the Eleven and said to them:
"Go into the whole world and proclaim the Gospel to every creature. Whoever believes and is baptized will be saved; whoever does not believe will be condemned. These signs will accompany those who believe: in my name they will drive out demons, they will speak new languages. They will pick up serpents with their hands, and if they drink any deadly thing, it will not harm them. They will lay hands on the sick, and they will recover."
The image above is by Parmigianino (1503 - 1540). The painting lives at the Kunsthistorisches Museum in Vienna, Austria. (Many paintings of St. Paul's conversion show him falling from a horse even though no equine are actually mentioned in that scripture passage.)