Abseiling is the controlled descent down a rock face using a rope. Climbers use this technique when a cliff or slope is too steep and/or dangerous to descend without protection. Abseiling can be an activity by itself, but is usually a part of more adventurous trips like canyoning or caving. The links for canyoning and caving below also have good information about abseiling.
Wikipedia has general information about equipment and styles.
Kayaking/Canoeing/Rafting is travelling across water in a self-powered boat. This may be a single day’s activity or one spanning multiple days where camping gear is carried in the boat.
Wikipedia has general information about types of kayaking.
The NSW Department of Industry maintains a number of canoe trails across the state.
Canyoning involves walking, scrambling, abseiling and swimming through deep gorges sliced through rock over thousands of years. While every canyon is different, most are dark and sunless, with moss covered walls and swirling shapes caused by the relentless scouring by water.
Oz Ultimate provides technical advice and descriptions of canyons near Sydney.
Blue Mountains Canyons has wonderful photos and other information about canyoning.
Fat Canyoners is an active group of canyoners.
Liloing is the art of enjoying oneself paddling down a river on an inflatable rubber mattress, shooting the odd friendly rapid. There is usually a destination which may be some way downstream on a river or creek, and there may be a walk to the start and a walk out at the end.
Melbourne Bushwalkers has a useful introduction to liloing.
Brisbane Waters Outdoor Club has a useful list of equipment for liloing.
Caving (known in some countries as spelunking, potholing or caverneering) is the exploration of underground passages, tunnels, caverns and shafts. There is high diversity in the caves and caving areas around NSW. Some caves are warm, some cooler. Some caves are dusty, some muddy. Some caves consist of large passages you can walk through, others are more suited to crawling and pulling yourself along the ground. Often a single cave can have all these features.
Speleology is the scientific study of caves and the cave environment. Many clubs contribute to the knowledge of cave systems.
Wikipedia provides a general introduction to caves and caving.
Sydney University Speleological Society has a handbook for beginners.
Skiing originated as a means of transport in cold countries, where it was used for moving from one place to another. Nowadays, skiing is mostly a recreation. There are several forms. Alpine (or downhill) is practised at resorts where skiing is on defined routes. Cross-country or nordic skiing can be done anywhere there is snow. Trips can be just a few hours or up to several days where you camp on the snow.
The Nordic Ski Club of NSW is dedicated to cross-country skiing.
Cycling is usually done in the bush on mountain bikes, but is also done around town. Bicycle tours can be a wonderful way to travel around NSW.
Bicycle NSW represents bicycle users in NSW, and provides useful information on cycling.
Cycle Trails Australia is a guide to bike touring across Australia.
Overseas trips can expand the wilderness experience, and expose walkers to scenery, wildlife, history and conditions not found in Australia. Walkers can travel overseas individually, but may prefer to travel with others for safety reasons. Bushwalking clubs often arrange extended trips for like-minded people to places like New Zealand, North America, Nepal and Europe.
Bushwalk.com has a section for discussion of travel overseas.
One of the most wonderful experiences for bushwalkers is to be out in the bush with a bunch of like-minded people. But bushwalkers also get on well in normal life, and often engage in social activities like going to the pub, dinner at a restaurant or club, concerts and theatre parties.
Bushwalkers have an attachment to the bush, and support many of the major conservation issues in the state. Whether this is demonstrations such as the recent Hunting in National Parks campaign, volunteering with the NSW National Parks and Wildlife Service, or just helping with local Landcare, bushwalkers are there!