It wasn't until this summer that I began drinking iced coffee. I found the perfect bean to use and now I drink iced coffee more than I drink hot coffee.
The Best Beans
There are a number of roasters (mostly independent ones) who roast coffee specifically for the purpose of brewing an iced cup. One roast that I have found to be fantastic is roasted by Metropolis out of Chicago. It's their Prospero Summer Blend. These beans brew an alright hot cup: a little heavier and darker than expected but good. Then I iced the coffee and it was a whole new world. It tasted more like coffee than it did when hot and it was crisp and clean. Just adding ice didn't make it as good as it would get though.
I have tried using regular beans (I used a French Roast from Trader Joe's) but it simply doesn't taste as good. If you are limited in your coffee supply I recommend using a lighter blend. I think that a great glass of iced coffee is made with a medium roast. A light roast will be thinned out too much by the ice. A darker blend will not have the flavor or drinkability of a medium roast.
Icing the Coffee
Be sure to use clean ice. Ice made in your freezer typically contains impurities. As the ice melts these impurities could add an undesirable film to the coffee. Gross.
After you've added good, clean ice, it's time for the milk. I like to use just one tablespoon for every glass (6-8 ounces). A little milk goes a long way in lightening the color and cutting the bitterness of the coffee. Also, I use 2% milk. I would imagine that skim milk would lead to a thinner blend.
If it's a Saturday or Sunday, and you're not going to be driving soon, I highly recommend adding a bit of whiskey. The whiskey that I recommend and use myself is Jameson. I typically add about twice as much whiskey as I added milk. This amount won't make the drink too acidic.
I find that iced coffee has a bold, light flavor. For those who prefer a sweeter or earthier flavor you may want to try adding some things.
Sugar: If you want a sweeter drink I recommend adding regular white sugar or 'sugar in the raw'. Begin by adding a small amount and increase to taste.
Cinnamon: Adding this spice will give the coffee a nice Christmas-y flavor. As with the sugar, be sure to only add a small amount. With any coffee drink, a little cinnamon goes a long way.
Nutmeg: You can find whole or ground nutmeg in the spice isle at the grocery store. In the winter I shave a little nutmeg into the grounds of my coffee prior to brewing sometimes. I find nutmeg is better in hot coffee than in iced but if you're curious, try it out.
Coffee Cubes: If you really want to coffee-up your iced coffee try freezing coffee into ice cube trays and using those cubes for your iced coffee.
Keep toying with your recipe until it is just the way you like it. Enjoy your summer coffee!