MarlinTPC is the software package being developed in the LCTPC collaboration.
The MarlinTPC meetings happen about once per month and are held over EVO, respectively over a phone bridge to the EVO system. A list of all meetings including the presentations and agendas can be found in the linear collider INDICO pages:
List of MarlinTPC and other TPC R&D meetings.
Another way of getting in contact and dicussing things with the MarlinTPC developers is the Tracking & Vertexing section of the linearcollider forum.
Special software and analyis related meetings like the Analysis Jamboree and the MarlinTPC Working Meeting are listed in the Reviews and Special Meetings section.