what goes up must come down.. this is as true in economics as it is in physics.
and the larger the imbalances are during the "good times", the harder the fall will be. the dot-com boom turned into a market bubble and... *pop*.. the great depression also had a market bubble, fueled by a massive credit bubble..
what do we have now? for starters, bush has bestowed $3 trillion (and counting) in new debt to the american public. he's done nothing to reform social security because if the investment bankers can't have their hands deep in the action, then there can be no deal as far as he's concerned.. and his "reform" to medicare estimated to cost another
$1.2 trillion. and that's just public debt - how about all those people taking out variable rate mortgages who aren't going to be able to sell those houses anytime soon? the thousands of college students out there drowning in debt.... our massive companies on the verge of bankruptcy, from the airlines, to auto manufacturers, etc... total corporate debt is about 50% of gdp right now..
the fact that we're in a massive credit bubble is undeniable - and no amount of partisan cheerleading can negate it's veracity.
as to what you can do to protect the assets you currently own... first off, if you truly believed that we will experience a crash, i would certainly stock up on lots of non-perishable commodities. as much as is reasonable and possible. should we experience a crash, you will be forced to pay out the ass for your most basic needs - so better to be prepared in advance.. get some source of power, canned goods, water, etc... and as far as your monetary assets are concerned.. you could buy precious metals - which i would advise against because their prices will be very inflated by the time you finally buy them (and i'm not convinced that they will be readily accepted as a form of payment). you could convert your dollars into euros or yen.. or, you could buy a load of TIPS (treasury inflation protected securities) and hold out until the government manages to salvage our currency. TIPS only shield you from changes in CPI though, and CPI has been found to understate inflation rates...
there is no perfect answer, but those options would be infinately better than staying in equities or cash.