Wreath - I found this awesome rectangle wreath for $7.99 at the craft store. Plus I used a 40% off coupon!
Gourds - Found bags of approx. a dozen of them for $3.99. The smaller variety is best due to the weight. Ones that are too heavy will be too difficult to fasten to the wreath.
Wire - Found it right by the eye screws in the hardware department. You will need to make sure that it is a thick enough gauge to hold the weight of the gourds.
The How To
1. Screw the eye screws into the back side of the gourd (the side that you don't want showing).
2. Using the wire, fasten gourds on wreath. Be sure to wrap several times and tightly as the gourds are a bit heavy.
And that's it. There is nothing to it. I hung this in our foyer on a closet door. I will be sure to keep an eye on the gourds since I punctured them using the eye screws. If the gourds start to deteriorate, I will take it outside and hang it out there or dispose of the gourds. I also plan to keep the eye screws, wreath and wire (if I can salvage some) and re-do one for next year. The gourds are cheap enough that it's not a big deal.