I'd say a summer pudding. Easy and delicious, you can serve it with some creme fraiche or whipped cream. Some of the recipes use a pudding basin, but a bowl works fine (that's how I make mine). Here's a few recipes to get you started:

http://becksposhnosh.blogspot.com/2006/07/recipe-for-summer-pudding.html

http://www.davidlebovitz.com/recipes/sum_pudding.html

http://www.epicurious.com/recipes/food/views/Summer-Pudding-with-Blueberries-and-Raspberries-238934

Oh, and could always make them in individual cups and turn them out onto plates to serve them.

I think strawberry pie is always pretty mediocre, and they are dull when cooked. Strawberries are much better fresh. I'd do a pavlova or a shortcake.

I tend to agree about strawberry pie never living up to expectations. The only baked fruit dessert I really enjoy is cobbler, which can be divine with vanilla icecream. If you happen to have blackberries or blueberries it's a great idea.

Strawberry shortcake is always fun and usually unexpected. Make your own shortcake for sure (basically slightly sweet biscuits, quick, easy, and cheap!

Or just toss berries on ice cream. Always pretty, customizable, cheap, and could not be easier.

What about a trifle with angle food cake, whipped cream, vanilla pudding and berries. I've done one with chocolate cake soaked in kalua, choclate pudding, whipped cream and strawberries for many BBQs, its always a big hit.

Cook's Illustrated's Key Lime Pie bars -- they're easy and terrific. This version of the recipe is slightly different, but it's free:

http://judyskitchen.blogspot.com/2009/04/cooks-illustrated-key-lime-bars-adapted.html

I think the main difference is that the Cook's Illustrated version doesn't have any whipped cream topping.

For something so absurdly simple, this has always been a huge hit with guests.... Peaches under meringue.

http://www.epicurious.com/recipes/food/views/Peaches-Under-Meringue-354492

You can roast, poach, marinate the peaches however you want to give them any extra flavor or softness you prefer, and then a little meringue, some flame, and then let them chill in the fridge for a cool desert or fresh from the oven for those colder nights.

They look beautiful, take about 4 minutes of work to make, and will cost you a few dollars for fresh peaches and eggs.

God I miss you, Gourmet magazine...

I was going to post a link to this recipe under the pound cake article, but I think it's a good choice for your summer dessert, too. Although it is not "cool", it is served at room temperature and has such a wonderful citrus-y flavor...plus it would go well with some lemon or vanilla ice cream. I made this for Easter and everyone loved it. Good luck!

http://www.ezrapoundcake.com/archives/5640

I second the idea of cake, including pound cake: bake the berries into the cake or spoon macerated berries on top (or both). If you can, serve with ice cream, whipped cream, or creme fraiche. Or, for something really no-fuss, how about just lightly sweetened strawberries? Brown sugar has already been suggested, but strawberries are also delicious with balsamic vinegar.

Strawberry/blackberry pie sounds great, though I know black berries aren't in season here yet -- rhubarb sure is though! Perhaps strawberry rhubarb pie or crumble is in order?

I love sweet yoghurt desert as a light option at the end of a dinner party. My favorite is Sweet Saffron Youhurt (http://www.bbc.co.uk/food/recipes/database/sweetsaffronyoghurts_86570.shtml). It is easy to make and you could easily swap the nuts and pommegranate seeds suggested for the topping with seasonal berries.

I would go with a mixed berry pavlova (giant meringue), emphasizing the strawberries. Here is a great recipe from Ina Garten that I've made for many parties and it's always a hit: http://www.foodnetwork.com/recipes/ina-garten/mixed-berry-pavlova-recipe/index.html

Oh - and if you do a pavlova it should be assembled at the last minute.

Here's another vote for trifle: you get your cake, you get your berries, and you get something creamy to hold them together.

Try a lemon cake in the trifle (or a ginger cake with some lemon in your creamy filling) to spice things up a bit.

Easy! Summer pudding.
It's a doddle, there's no messing about with baking and potential kitchen disasters and nothing beats it for a summery pudding. Big dollops of mascapone on the side are needed too!

My vote? Dorie Greenspan's Sweet Cream biscuits split and topped with sugared fresh berries and then pour heavy cream over top. Soooo good!

Or even just fresh berries with sweetened heavy cream. It's seriously delicious and decadent and light and easy all at once. Just let people pour their own heavy cream and you'll be just fine. :)

If it's a grilling party I'd go with the theme and grill fruit. Use halves of peaches/plums or pineapple rings. After a few minutes, the sugars in the fruit carmelize and it's delicious. Serve in a bowl with a scoop of vanilla ice cream on top.

What about an ice cream pie? Epicurious has some great ones.

Key Lime pie or tarts.

I'm a huge fan of this chocolate-ricotta icebox cake. Easy, delicious, and very impressive-looking! And it is great to make ahead.

http://www.marthastewart.com/recipe/chocolate-ricotta-icebox-cake

Homemade angel food cake with strawberries that have been sliced, lightly sugared and had time to juice up.

Grill some pineapple spears and serve with berries and lime juice and...

Rhubarb! Rhubarb! Rhubarb!
I don't like pie, but I will eat any pie with rhubarb!

Perhaps a fruit pizza? It's basically a shortbread type crust, topped with sweetened cream cheese mix and sliced fruit, drizzled with reduced fruit juice or chocolate sauce. Lots of variations to be had, and it is a very nice summer dessert.

It's a BBQ, why not more hand held yumminess? Ice cream sandwiches. But make your own sorbet...dead easy and lots of recipes out there. I tried a chocolate one last year (can't find it now) that was incredibly lovely on peanut butter cookies. We've also enjoyed lemon sorbet on gingersnaps and raspberry sorbet on lemon shortbread cookies. I find a crumbly almost crunchy cookie holds up best to the softness of a good sorbet. You can even do it the easy way and BUY the sorbet and cookies...just put them together and freeze until serving time!
Happy grilling!