On the old psychopy-users group, mention is made of a script that can be used to run multiple experiments one after the other (see post from Jeremy below).
The link is now deprecated - I was wondering if a similar script exists anywhere else?
A cross-platform way to do this is to manually compile your individual Builder experiments into code, and save the code for each experiment as a .py file. (Save them all into a new clean directory–just one directory for the whole set, not a new one for each script.) Then download a short python script, launcher.py, from here: https://gist.github.com/4076435 Save it in the same directory as the .py files (and have nothing else in the directory). Then execute launcher.py, e.g., from the command line: python launcher.py
That will find and then call all of the PsychoPy experiments in order. You can name the files in such a way that it controls the order in which they will be run (they get sorted by file name). Its also easy to randomize the order instead.
Only tested on a mac (and not thoroughly tested).