Free software for merging clips?

I’m having a problem editing my home dv and authoring it to a DVD. I have already converted to .vob and have 12 chapters to burn. However, within each chapter there are several clips. The FF/advance feature will go to the next clip instead of the next chapter so I assume I need to merge the clips within each chapter. At what point during the encoding process should this be done (as an avi, mpeg2 or vob?). If I can merge at the vob stage, what free software can I use?

There is a free 30day demo of DVDLab that you can use to author your vob files and set what ever chapters you want.