For your Cascades, I love them in an american-style pale ale. Here's a link to a recipe I recently did - I haven't put on it in the HBT database yet, because I'm not sure if its in its final form, but you'll get the idea . . .http://www.singingboysbrewing.com/WPA-Wheat-Pale-Ale.html
You could definitely go all Cascade in this recipe or one like it.
For the Hallertauer and Spalt, you could use them in a lighter beer - a pilsner, a cream ale, a kolsch, or a light hybrid like this http://www.homebrewtalk.com/f62/drinkability-isnt-word-154954/
FWIW, I really enjoy taking the ingredients on hand and figuring out what to brew with them - its great to have some bulk grains in the bins and some hops in the freezer!