I try to avoid shorting the market, but if you feel compelled to do so, I recommend QID and SDS. QID is an ETF that shorts the Nasdaq. It is the anti-QQQQ's with a kick in that it magnifies the movement in QQQQ by a factor of 2. So for example, a 1% down move in QQQQ implies a 2% gain in QID. Similarly SDS is QID's counterpart for the S&P 500. If you think the stock market is heading lower, and I don't argue that, I recommend you play these for the short term.
-- Faisal Laljee
Full Disclosure: I do not own any shares of QQQQ, QID or SDS but my position might change anytime without notice.