Is there a recommended format for multi-line imports?

I would go with the parenthesis notation from the PEP328 with newlines added before and after parentheses:

from Tkinter import (
    Tk, Frame, Button, Entry, Canvas, Text, 
    LEFT, DISABLED, NORMAL, RIDGE, END
)

This is the format which Django uses:

from django.test.client import Client, RequestFactory
from django.test.testcases import (
    LiveServerTestCase, SimpleTestCase, TestCase, TransactionTestCase,
    skipIfDBFeature, skipUnlessAnyDBFeature, skipUnlessDBFeature,
)
from django.test.utils import (
    ignore_warnings, modify_settings, override_settings,
    override_system_checks, tag,
)

Personally I go with parentheses when importing more than one component and sort them alphabetically. Like so:

from Tkinter import (
    Button,
    Canvas,
    DISABLED,
    END,
    Entry,
    Frame,
    LEFT,
    NORMAL,
    RIDGE,
    Text,
    Tk,
)

This has the added advantage of easily seeing what components have been added / removed in each commit or PR.

Overall though it's a personal preference and I would advise you to go with whatever looks best to you.

Your examples seem to stem from PEP 328. There, the parenthesis-notation is proposed for exactly this problem, so probably I'd choose this one.