How many people are you expecting? Is it formal or more informal? Since it is summertime, I would suggest the following...
Mini Quiches: This is a yummy recipe: http://www.bettycrocker.com/recipes.aspx/garden-phyllo-quiches
Cupcakes: Use the bride's colors for the wedding to make cupcakes. If the colors are white and lavender, make white cake with lavender frosting. You could just use boxed cake mix and food coloring to keep it simple. You can also add pureed fruit, flavored extract or other ingredients to add color and flavor. If you get really creative, write the bride and groom's initials on the cupcakes!
Finger Sandwiches: simply make several normal, but not too tall sandwiches with two regular pieces of bread - crusts removed - and then cut them into quarters diagonally. Secure each mini-sandwich triangle with a toothpick. These look fancier with any kind of simple sandwich: PB & J; chicken salad; egg salad; cucumber, yogurt and dill, brie and cranberry, anything!
Pesto Pasta Salad: Combine any short pasta (penne, rotini, gemelli, cavatappi) with pesto (homemade, canned or from a mix), sundried tomatoes, black olives, chunks of mozzarella cheese, shredded or shaved parmesan cheese and anything else that you think would be tasty in there, like zucchini or halved fresh cherry tomatoes. Yum!
Fruit Salad: Cut up and combine any fruits and berries that look exceptionally tasty in the store when you go shopping. I don't even add any kind of sweetener, sauce or glaze. Everyone loves fruit salad and eventhough it is SO simple to make, people always seem to appreciate it and prefer it over store-bought.
Veggies and dip - simple, easy and always appreciated by guests
Mango Green Tea: Brew a pot of green tea or regular iced tea and combine it with a prepared quart of Crystal Lite Mango Green Tea and float some sliced limes and lemons. This is really tasty!
I hope this helps!!