This is the generator used to build instances for works on uncertain durations and those making use of Logic based Benders' Decomposition (i.e. Conditional Task Grapha and multi-stage LBBD). A paper describing some of the features of a flexible graph generator was presented at the ICAPS07 workshop "Scheduling a scheduling competition".
The generator is designed to produce Task Graph representing "realistic applications"; options are customized via a configuration file, passed to the software as a command line argument. The generator can label arcs and nodes in the graph wit a user-defined set of attributes; attribute values are obtained by combining randomly generated numbers and other attributes values; this allows to state (e.g.) that a task maximum duration is always larger than the minimum duration.
The code for the generator is available for download. Be careful, however: it is not well polished and there is no documentation at the moment.
UPDATE: there's guy at our lab working on a brand new graph generator; I'll let you know when it is available.