A friend of mine is studying glaciology in New Zealand and he is working there with data taken with the GeoTIFF format but needs it in NetCDF to put it into the model they are using at the university so he wrote a little C program to convert between the two using the libgeotiff and NetCDF libraries.
I got permission for him to put the program out on the net for others who are interested to have a look at it and also to put a GPL license on it. You can find it here along with a small makefile to compile it (read the makefile before you try it, it might not work on your computer), or you can just compile it with your own compiler.
At the moment the software is limited to his specific needs but it is well commented so people should not have to much problem in adapting it to ones needs. Perhaps we will work on it more in the future and get it to be more general.