Someone just asked me about moving a site with subsites to a new location, but didn’t have details.
Without knowing the situation, here are some of the countless options with considerations:
1) Site Collection level backup and restore
only applies if the subsite is a site collection and you can overwrite the exisiting top level site
use stsadm -o backup and stsadm -o restore
2) stsadm -o export and stsadm -o import
may require manual touch up
but works on site level, not limited to entire site collections
3) save site template with content
one site at a time
limited by size of the content
The default limit is 10mb for one template, but the limit can be changed