Poison ivy: #6, #7, #13, #15, #16, #17, #20, #21, #27.

your link. Some of those look like berry vines. PI doesn't have any thorns.

Thanks, esh_ga:

So it look like the "thumb" rule is the key, whether the leaf is jagged or smooth edged?

Not at all, some poison ivy leaves have very scalloped edges.

Kudzu leaves have a thumb. But it is cause for suspicion!

This site has many photos of "mitten-shaped" PI leaves:
http://grandpacliff.com/Plants/PoisonIvy.htm

I've never seen those anywhere, but people keep saying they're the norm. I have no idea where they're the norm (I've lived on the same property with major amounts of PI in CT, OH, and NC, and regularly encountered it in various parts of IL).

Poison ivy leaves: The outer two leaves have a scalloped outer edge and a smooth inner edge. The center leaf is the same on both edges.

Unfortunately, PI has quite a variety in its leaves. The edge can vary from almost smooth to quite toothed and at different stages of its development can be shiny or matt. Often, but not always, there are reddish tints to the leaves or the stems.

Strawberry (always 3 leaves, sharply & regularly toothed, no thorns, fuzz on stems and reverse of leaves): 2, 8, 9, 10, 18, 19, 22, 24

PI (always has 3 leaflets, with the center leaflet having a longer 'stem'): 6,7, 13 (center), 15, 16, 17 (though also has greenbriar with thorns), 20, 21, 26, 27

Rubus (dewberry, blackberry; has thorns): 1, 4, 5, 6, 11, 13 (on top edge), 14, 23, 28, 30, 31

Bittersweet: 23 bottom left, 24, 25

Virginia creeper (5 leaflets): 21 lower left, 25 lower left

Something in the nightshade family: 26

Convolvulus/ bindweed: 29

12 has PI at center top sort of dpwn under and on left edge, rubus in the middle, bittersweet on right.
15 has mostly PI, but probably Viburnum on right and greenbriar on top edge.

Please take a look at 2 more photos of leaves from the same plant.

https://www.dropbox.com/sh/suxjz6snmkqsn9u/TSHfXhdDOZ

#32 has mittens and looks like PI, but the same plant has #33 which has 5 leaves.

PI or Not?

30 through 33 are definitely not PI.

The stems have thorns -- PI has no thorns.

The leaf edges are finely and sharply toothed -- PI leaves never have so many teeth, or teeth that sharp.

The leaf surfaces are corrugated (not a correct botanical term!) in a way that PI leaves never are (more sharply/abruptly/angularly corrugated than PI; PI leaf surfaces are flat-to-wavy, while 30-33 look like they've been creased).

I suspect 30 through 33 are all berries. Other people can tell you which family of berries (nhbabs says 30 and 31 are rubus).