I have made a video composed of several videos with transitions etc, but they all have a 80px black strip on the top and bottom, and I'd like to remove it (so that the video's height is 160px less). How do I crop the video?
You can group your clips in to a meta strip by selecting them and hitting Ctrl G. If you want to edit the clips inside it after grouping them, select your meta strip and hit Tab.
You can now apply an Image Crop to the meta strip in the properties panel (N). Be sure to check Image Offset. You will also need to change the render dimensions to the correct size.
You can avoid the need to crop in the video sequence editor entirely by performing the crop in the render dimensions. Simply set the dimensions to the target aspect ratio for you image.