resources.py

class EntryResource(ModelResource):
    user = fields.ForeignKey(UserResource, 'user')

    class Meta:
        queryset = Entry.objects.all()
        resource_name = 'entry'

    def dispatch(self, request_type, request, **kwargs):
        username = kwargs.pop('username')
        kwargs['user'] = get_object_or_404(User, username=username)
        return super(EntryResource, self).dispatch(request_type, request, **kwargs)

urls.py

# urls.py
from django.conf.urls.defaults import *
from myapp.api import EntryResource

entry_resource = EntryResource()

urlpatterns = patterns('',
    # The normal jazz here...
    (r'^blog/', include('myapp.urls')),
    (r'^api/(?P<username>\w+)/', include(entry_resource.urls)),
)