kinfit and mkin provide calculation routines based on the FOCUS Kinetics Report (2006). In kinfit, only kinetic models for simple degradation datasets are included. In mkin, there is no theoretical limit for the number of compartments or metabolites to model. gmkin provides a graphical user interface for mkin.
Please note that no warranty is implied for correctness of results or fitness for a particular purpose.
The mkin package which can fit complex degradation models to degradation data has a documentation page which also contains installation instructions.
An overview of the current capabilities of the kinfit package (rapid and simultaneous fitting of the kinetic models recommended by the FOCUS group for parent only) is given in the kinfit documentation page which also contains the package vignette.
Please refer to the project homepage for further information on the r-forge project.