gistfile1.py

#!/usr/bin/env python
# encoding: utf-8

class Base(object):
    pass

class Eins(Base):
    pass

class Zwei(Base):
    pass

class WasAnderes(object):
    pass

def subClassesOf(BaseClass, scope=None):
    if not scope:
        scope = globals()
    map = {}
    for name in scope:
        obj = scope[name]
        if ((type(obj) == type) and (issubclass(obj, BaseClass)) \
            and (obj is not BaseClass)):
            map[name] = obj
    return map
          
print subClassesOf(Base)
# {'Eins': <class '__main__.Eins'>, 'Zwei': <class '__main__.Zwei'>}