My first multisport event was a bike leg in a duathlon at Eastern Creek in 91 or 92 (memory hazy). I quite like them but they dont seem to be as popular now. Run/Bike/Run in various distances. The Australian Duathlon champs are on in Newcastle this weekend but I canned my entry due to the closeness of GC marathon and travelling. Besides we have a club one on next week that only takes an hour or so to do.
There used to be a lot over winter...There was Panthers and Dapto...In fact one of the Dapto ones is the only DNF I have ever had in more than 200 tri's/duathlons races....Some lowlife poured a heap of tacks over the road about half way out...I usually now always carry a repair kit just in case.
I think they should put more of them on. There are a lot of people who dont like swimming but like to run and ride. Particularly teams events to encourage the novices. They got me into multisport so it could help boost flagging numbers in tri's etc experienced in NSW...Qld and Vic seems to be going quite strong tho.
Your best bet is to join a tri club as they usually hold them over winter...Your profile doesnt indicate where you are from but if you use this link
http://www.triathlon.org.au/ it can direct you to your state organisation. If you join a club the club races are usually only a few $ . It is the staged events which get a little more expensive.