I have.
Red Nose Day - I woke up 4am in the morning (lol it was terrible but worth it nonetheless) to catch a train with a bunch of friends over to Martin Place. We spent the entire morning there until 9am standing around Pitt Street Mall and other major places nearby to sell charity products on the streets. We also met Koche and Mel from Sunrise, they were lovely. =)
Red Shield Appeal - Also early morning where a friend and I went to the Burwood area (They do most of suburban NSW) for door-to-door knocking. Raised about $800. Very good cause.
Just Enough Faith - Feeding the homeless. They grab you for one night every once in a while to go out to Belmore Park and nearby areas where you are responsible for certain tasks in feeding homeless people. Usually you're in a trailer-like place responsible for preparation or distribution of the food.
I guess most of my co-curricular stuff is charitable but there are numerous youth festivals every years (in particular the south west area) where they need volunteers to help with day-time activities and helping out. It's good fun and looks good on your resume. =)