Emily at Inhabitat does a terrific post that we should have thought of and called "how to green your holiday," suggesting:
-chose your food wisely; (avoid foods produced or raised on factory farms)
-use eco-friendly picnicware; (or we might suggest renting real plates and silverware)
-find alternatives to fireworks; (colorful decorations like ribbon streamers)
-use a greener grill with sustainably produced charcoal;
-when it is all over, recycle the garbage.
Not too many people thought that fireworks are history in our last poll, but perhaps Treehuggers somewhere are celebrating a green July 4: