# models.py
from django.db import models
from django.utils.translation import ugettext_lazy as _
from django.contrib.auth.models import User

class Test(models.Model):
    user = models.ForeignKey(User, verbose_name=_('user'))
    text = models.CharField(_('text'), max_length=100)
    
    def __unicode__(self):
        return self.text

#admin.py
from django.contrib import admin
from test_app.models import Test

class TestAdmin(admin.ModelAdmin):
    list_display = ('user', 'text', )
    search_fields = ['text', ]
    
admin.site.register(Test, TestAdmin)

# форма
class TestAdminForm(forms.ModelForm):
    class Meta:
        model = Test
        exclude = ['user',]

    def save(self, commit=True, *args, **kwargs):
        inst = super(self.__class__, self).save(commit=False)
        inst.user = self.current_user
        if commit:
            inst.save()
        return inst

# admin.py
class TestAdmin(admin.ModelAdmin):
    list_display = ('user', 'text', )
    search_fields = ['text', ]
    form = TestAdminForm

    def get_form(self, request, obj=None, **kwargs):
         form = super(self.__class__, self).get_form(request, obj, **kwargs)
         form.current_user = request.user
         return form

    def __init__(self, *args, **kwargs):
        super(TestAdminForm, self).__init__(*args, **kwargs)
        self.fields['user'].initial = self.current_user
        self.fields['user'].widget = self.fields['user'].hidden_widget()