(from developer's page):
SplitFuse is a tool that can split movies into multiple segments or fuse together movie segments that have already been split apart. SplitFuse is ideal for fusing segmented movies that you have downloaded from the web or splitting apart movies for web distribution. It is also useful for splitting DV movies into 2GB chunks compatible with iMovie. It has a number of useful features:
Split movies into clips defined by you, into any number of equally sized segments, or into segments of a specific length
Offers complete control over the names of split segments
Fuse together any number of segments and save the movie as a self-contained movie or as a movie that references the fused segments
SplitFuse is super cheap. Other programs that do the same thing would like to charge up to $20 USD! SplitFuse is just $9.95 USD!