A Better Django Admin ManyToMany Field Widget

you could try using a raw id in the admin. and the django docs: http://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.raw_id_fields

if you are looking for something with auto-complete you might want to look at this as a starting point http://code.djangoproject.com/wiki/AutoCompleteSolutions

and finally a very simplistic inline Example:

models.py

class SomeModel(models.Model):
    users = models.ManyToMany(User)

admin.py:

class SomeModelAdmin(admin.ModelAdmin):
    raw_id_fields = ("users",)

Try using the filter_horizontal attribute on your admin class, for example:

class SomeModelAdmin(admin.ModelAdmin):
    filter_horizontal = ('users',)

As mentioned in the documentation, "adding a ManyToManyField to this list will instead use a nifty unobtrusive JavaScript "filter" interface that allows searching within the options". filter_vertical does the same thing with a slightly different layout.

I haven't actually played with it but I found this promising looking library referenced elsewhere.

It appears to do exactly what I wanted. Rather than loading the entire list of related objects (regardless of how many there are!) and presenting you with a picker to select a few of them, as filter_horizontal does, it presents a search/filter box and uses typeahead/autocomplete calls to retrieve results dynamically. This is great for the case where you have maybe 5000 users and want to pick 3 or 4 of them without waiting for 5k <option> elements to download and render.