That's covered under the rules for Sunder. I could cut and past it from the SRD, but so can you, and since you want to know and I'm not that curious, the ball's in your court there my man.
As for other methods, there are still Item saving throws somewhere (DMG?). There used to be a rule that a nat 1 on a Save meant you had to save for your items. Disjunction targets magical items, but it may be a little over-the-top ot start centering it on 8th level parties. Dispel Magic can knock items out for a period of time, and you can always go with the classic Dead Magic Zone, which doesn't destroy items but does nullify them when you're in there. Depending on how you interpret Psionics, DMZ's are either a good place for your psionic monsters to set up shop or (if you take psionics as magic) a good place for the magically vulnerable types (big scary monsters with low ref and will saves, like giants) to hide out.
Also, there's the whole category of monsters that do this. Rust Monsters are the poster boy (bug). There was another one an old GM of mine got out of Dragon Magazine, an orb of light that flew around and "ate" magical energy, essentially draining magical items. High level parties scattered away from these like cockroaches. Someone around here will know what those are called.
Also, a good ship sinking and a rigorous and keen-eyed enforcement of the swimming and encumbrance rules might help out with getting pc's out of excess gear, but they're getting past the level where that will work.