The 5 basic areas of on-going competition are:

UGV (autonomous/unmanned ground vehicles),

UAV (unmanned air vehicles), 

ARV (aerial robotics — yes, different from UAV),

AUV (underwater vehicles — not to be confused with UAV , and  

ASV (surface vessel).

All comps are run more-or-less annually by the Unmanned Vehicle Assoc  (AUVSI) and US Navy Engineers, around mid-y.

I'm presently (and will most likely continue to be) a member  of the AUVSI San Diego chapter.

The comps are open to "students",  typically teams, but it is not unknown that entries from businesses or some combo of business/student input get entries together.  The overall aim of the comps, after all, is to foster future engineers intertested in the area.

Some comps have nominal prizemoney. Some have facilities for funding student projects (e.g. the AR comp).

Each comp involves having a vehicle or robot complete a multi-part "mission".  Mission requirements increase in difficulty from year-to-year.

Entrants are given an overall view of the mission area prior to comps, but part of the comp includes a "pre flight" time — typically a couple of days — to acclimatise robots to the specific course.

The locations, missions and specific rules for each comp vary but the common thread in each is the requirement for autonomous operation:

The entries are not remotely controlled but are programmed to sense their surroundings and respond accordingly, independent of any external control by an operator.

Here are the various basic web refs:

Ground Vehicles:

http://www.igvc.org/objective.htm

http://www.igvc.org/rules.htm

Air Vehicles:

http://www.navair.navy.mil/pma263/seafarers/rules/rules2009.pdf

Aerial Robotics:

(comp rules):

http://avdil.gtri.gatech.edu/AUVS/CurrentIARC/FutureEventInfo.html

http://avdil.gtri.gatech.edu/AUVS/2000AerialRoboticsCompInfo.html/2000EventInfo.html (link farm):

http://avdil.gtri.gatech.edu/AUVS/IARCLaunchPoint.html

(1993 vid):

http://avdil.gtri.gatech.edu/AUVS/93IARC.mpg

Underwater Vehicles:

(2007 mission):

http://www.auvsi.org/competitions/2007/Mission_Rules_Final_2007.pdf

(2008 mission):

http://www.auvsi.org/competitions/Mission_Rules_Final_2008.pdf

Current comp website:

http://www.auvsi.org/competitions/water.cfm

NOTE: US Navy engineers and some design facilities (e.g. harware library) are available to support UAV entries.

Surface Vessels:

(2008 mission):

http://www.auvsi.org/competitions/ASV_Mission_Rules_08_final.pdf

Current webpage (even up-comining next week):

http://www.auvsi.org/competitions/surface.cfm

While the surface vessel comp has been small in the past, one of the perks is availability of the San Diego Hilton's pool for testing prior to comp.

I don't know of any comp that has been run in Australia.

But I know that at least 1 Aussie uni have sent  a team over (I'm pretty sure it was a UWA entry for the AUV comp; but it's all documented there somewhere .

But just because it seems lists of entrants are groups of US-based college students, don't think it is limited to them.

If anyone is interested, we can "get creative". I've seen small businesses represented, and it may be possible to get an entry in under Ausrobotics itself.

And don't worry what the actual rules say. It's America. Everything's nogotiable and also somewhat depending on the audio volume.