Carlos Simpson has [written][1] a lot on this. 
[Nasatyr & Steer][2].
[Biquard][3]
[Konno][4]
All on basic constructions. Verlinde, Thaddeus and others on structural considerations.
Anything to do with modular or automorphic forms is also related. There is a lot, can you be more specific?

  [1]: http://math.unice.fr/~carlos/
  [2]: http://arxiv.org/abs/alg-geom/9504015
  [3]: http://www.math.jussieu.fr/~biquard/
  [4]: http://en.scientificcommons.org/918305