I don't really have anything to add to the list of gear, but I can certainly attest to the usefulness of some of these suggestions!
One festival in particular comes to mind, and it wasn't even that big (BWFR 2004), but the crowd was pretty wild that night. My rig was pretty simple, a Sharp mini-disc unit, a pair of Church-Audio pro-binaural mics and an ST-20 pre-amp, all attached to a 15-ft stand with an old-school stereo bar. There were two stages - a large tent stage, and a main stage, and the bands were playing literally back-to-back. Particle was playing under the tent, and I had made good use of the gaffers tape, securing my stand to a large support beam. Good thing, considering the number of folks who kept staggering by, always managing to find that beam with their hands as they tried to steady themselves. Also, the one time I walked away to grab a beverage myself, I come back and notice a couple of pairs of smaller mics clipped and duct-taped to various parts of the stand. Fortunately, the stand was so secured, that nothing really disturbed the recording, amazingly enough.
No sooner was that set over, and I high-tailed it out to the main stage, where Medeski, Martin & Wood were just going on. What a surprise to see the torrential downpour that had begun while I was recording inside the tent! Since I was camping, I actually had a pretty sturdy umbrella in my backpack, and the gaffers tape came in handy fastening it to the top of my stand. As a general rule, I always have a heavy-duty Hefty bag, a head-light and a mini-mag in my backpack anyway, so in this case the rig could stay dry, and I could actually see what I was doing in the midst of everything! I've learned at these shows to keep a few extra tent stakes with me to secure the mic stand in front of the main stage, and they really came in handy that night as well. Luckily, there was absolutely no wind, just rain so thick that I couldn't see beyond the umbrella, once I was set up and rolling. You might think that much rain would have made an obnoxious roar over the music, but I figured, hey - it's either going to work, or it isn't... might as well give it a shot. The incredible thing was, when I played the recording back later, all you could hear was the music, clear as daylight.
Considering that every other taper that night threw in the towel when they saw the rain, it almost sounds crazy now, thinking about it, but when I heard how good the recording turned out, I was glad I bothered to stick with it.