AVIDemux:
Load the movie,
Move to the start of a section you don't want,
Hit cursor up or down to move to the nearest I-Frame,
Control+PgUp to mark the start,
Move to the end of the section,
Hit cursor up or down to move to the nearest I-Frame,
Control+PgDn to mark the end,
Control+X to remove that section,
Repeat as necessary,
Save.
If you haven't made a cut on an I-Frame you will be warned.
Otherwise there's also
Lossless-Cut if you like funky interfaces.