Hold a "progressive" goal party
If you have a group of friends with the same goal who live in close proximity (or who can meet up comfortably in a third-party establishment), get them involved in a progressive goal party. The idea is to meet at one location, where you all complete one part of the goal as a group, then move on to the next (carpool or walk) to complete the second part, and so on. This can be extended to include shops and other buildings as well as houses. Be sure to have appropriate snacks, fun activities, etc., at each stop to make it a special day.
A good example would be a Christmas shopping/preparation party: Everybody starts at one house making lists, planning the day's activities and eating a light brunch. Next, hit the malls (or other predetermined shopping areas) together, making sure to help each other hunt down those hard-to-find items - and don't forget to stop by the coffee bar or other dining place to fuel flagging energy and regroup. Afterwards, it's on to the next house to wrap (and have a late lunch or early supper), then on to the next to bake cookies (don't forget the eggnog and late-night snacks!). It's good fun, great camaraderie, and everybody gets their stuff done and over with at one time.