Thanks for this tool, it's about the only such tool available in the first x pages of google, where x denotes the number of pages I can scan through before losing my interest ;)
I've got some remarks, questions and/or improvements.

First of all I'd like to point out that in the mean time, geopy has become available for 2.6 as well.

Second, adding the following lines before opening the cache file removes the need to manually initialize a cache:

#add 'import os.path' at the list of import statements
if not os.path.exists("cache"):
    cache = {}
else:

Third, you forgot to add the route of each car from its final pickup location to the destination. Within the routes function, change the lines

            for op in ops:
                paths[(cnode, ) + op] = duration(origin, cnode) + ops[op]
        else:
            paths[(cnode, )] = duration(origin, cnode)

to

            for op in ops:
                newpath = (cnode, ) + op
                paths[newpath] = duration(origin, cnode) + ops[op]
                if plan[1] != plan[0]:
                    paths[newpath] += duration(cnode, dest)
        else:
            paths[(cnode, )] = duration(origin, cnode) + duration(cnode, dest)

Fourth, I think it can be optimized greatly in space requirements if you don't return all possible routes in the route function, but only the most optimal route. I haven't tested this though, as I'm not sure that that would actually be correct. I think it is, because all options from a returned set op options are prepended with the same nodes.

Fifth, I changed some more code to make it more human readable, adding names of the passengers and drivers and outputting those instead of numbers and addresses. Interested in the code?

Regards,
Jelle

Also, this theme doesn't seem to support nested comments. I really like the theme, so I might try to modify it for support (if you have any advice on this, I'd accept it).