Simple easy, but very personal way to encourage your students. In the age of facebook, twitter, and texting, sometimes the old fashion written word makes a huge impact. This is fresh fun spin on the personal written message.
While students are at school make a quick trip to a couple of homes and write words of encouragement or a verse on their sidewalk or driveway.
For a little more excitement and fun get a group of students or even leaders and go out in the middle of the night. It is better more positive alternative to the old TP raid, but with same excitement and "risk" of being caught.
It also can be a way to let students know you miss them if they haven't been in group in a while, send birthday wishes or a get well soon. It can become an on going thing and a big deal among students to see who get "hit" next!