What's the most successful crunchy green salad to serve alongside this recipe -- one that's presentational enough for a dinner party? Would arugul...

I agree with June about the balsamic - it's very assertive, maybe not best with the ragu. I like the idea of roasted/braised carrots as an accompaniment - throw in a few parsnips if you want to vary it. I'd serve a simple green salad (bibb lettuce, maybe a handful of arugula) with a classic red wine vinaigrette after the ragu course - if you feel like fussing it up, offer a small slice of blue cheese (Roquefort, Gorgonzola, whatever your budget or taste allows) and enjoy it with the last of the red wine and bread. Then take a breather before dessert. (Though for me, the cheese would be dessert enough.)

Okay, call me old school, but I'd serve the sharper salad, after the ragu, and of course, one wouldn't drink wine with the salad at all. That's the way people have eaten for centuries, with good reason. ;o)

For the reasons cited by June, I would not recommend serving a crunchy salad with the main course. Instead, I think a good vegetable side dish or two would more appropriate. Roasted or braised carrots would complement the delicious main course you chose and perhaps a quick sauté of spinach in olive oil with garlic and 1-2 anchovies melted in to punch up flavor. A nice match of crunchy salad afterwards? Slivers of fresh fennel tossed in lemon juice; shards/curls of parmesan, salt and drizzle of very good olive oil. A crisp, but tender escarole salad would be another good choice: terrific with clementines or orange, thin red onion rings and creamy avocado.

FWIW, I find Balsamic Vinegar lends a very strong mote to a vinaigrette, and does not go well with most wines. We prefer citrus as the acid in most vinaigrettes, or a milder vinegar.

I'd put this http://food52.com/recipes/21569-crunchy-creamy-cucumber-avocado-salad over arugula + baby chard/kale. Earthbound Farms sells a mix called "Power Greens" that's full of flavor. Plus, you could make the cucumber and avocado salad a couple of hours before, plate the mixed greens shortly before your guests arrive. Easy! ;o)

if you want to put in some time, this salad always gets rave reviews when I serve it.
If you do not want to use only kale, you could add some butter or bibb lettuce for some variety: http://food52.com/recipes/14417-kale-salad-with-fried-pear-chips-and-toasted-walnuts

Doesn't fall in the typical crunchy salad but its so flavorful: http://food52.com/recipes/16940-april-bloomfield-s-lemon-caper-dressing

Check the comments for alternatives.

Oranges ( blood oranges if you can find them) sliced and arranged on a plate along with fennel and chopped onions dressed with a good oil and vinegar.

I'm thinking that a salad of kale or brussel sprouts might be a better match. An addition of citrus in the salad would be nice as well, bringing some freshness to the palate when eating the heavier ragu. Just throwing out some ideas!

I'd suggest that arugula, as the only salad green, is too delicate to pair with the ragu. (But the balsamic and pine nuts are fine.) Would suggest a sturdier green mixed in.