The Underworld LARP is an impressive endeavour with an equally impressive web-site. At another site that I believe is related, there's some juicy session reviews that give a sneak peek into what it was like to actually be there. This can be really help for LARP organisers, as well, as some of the bits and pieces are pretty true across the board.
Players like to be comfortable, to a point. If things start to hurt, they don't like it. If the weather is particularly horrid, think about what to do with those who push against the plot (especially in a horror game where the risk vs. reward might be a worse ratio than you realised). What might be fun the first time round (crawling through tunnels) can become painful the seventh time around.
I just wish there were more pictures of the events. I'm still just wrapping my mind around how modules work and while I know I lack the resources to properly throw a module-based LARP just yet I'd still love to know quite how they work.
Regrettably I don't think there are any module LARPs in Australia. By module LARP, I mean a situation where most of the players are doing their own thing together but were small groups can branch out to accomplish a specific task in LARP format. Generally when a small group branches out it often becomes tabletop (which is partly because in a World of Darkness LARP the rules are too technical to be modelled physically).
This isn't a bad thing and is most suitable for a modern LARP where the characters could go just about anywhere at the drop of a hat but it does limit my chances to understand how this other type of LARP works.
I also like how Underworld links racial abilities to costuming. Just as many boffer LARPs won't let you deal damage without a boffer weapon or won't let you be armoured without representative armour, so does this one require you to use some makeup or something similar to get your racial abilities. If you don't want to do this, you can always be human. While I don't think this is necessarily appropriate to all games (i.e. Changeling), I do think it works quite well in certain LARPs like this one. Their forums have some good advice on makeup and prosthetics as well.
There's also some neat phys-reps for traps. The pressure plate has to be the easiest, though I can't help but want one that makes a neat 'clicking' sound so you can put it under fallen leaves or something yet still know when it goes off.