truncated poisson in glm / glmmPQL

Hi

I'm a postgrad in ecology, and have recently started to use R. I'm planning 
to model various sets of animal abundance (i.e. count) data in relation to 
habitat data using glm's and/or glmmPQL's. However, some of my potential 
response variables have many zeros. From what I gather the "family = ..." 
option in the command line does not allow for the direct specification of a 
truncated / zero-modified poisson distribution. My problem is probably not 
uncommon, but I could not find anything on truncated poisson distributions 
in the R web pages or documentation.

Does anyone know of a bit of software that someone may have written to deal 
with this problem? I'm interested in modifications to the poisson as well 
as quasipoisson families.

Thanks a lot for your help - Joern.