* Chicago PMI unexpectedly contracts in September
* Energy rises after report lifts crude oil
* Cisco leads Nasdaq, semiconductors higher
* Dow up 0.1 pct, S&P off 0.02 pct, Nasdaq up 0.3 pct (Updates to early afternoon)
By Ryan Vlastelica
NEW YORK, Sept 30 (Reuters) - U.S. stocks were mostly flat on Wednesday, on a volatile last day of a strong third quarter, as a disappointing report on Midwest business activity was offset by gains in commodities and tech.
The Institute for Supply Management-Chicago's business barometer unexpectedly fell to 46.1 in September, a level that indicates a contraction in the regional economy.
The Chicago PMI's September level was below the consensus estimate for a reading of 52 and down from 50 in August.
While the markets initially fell on the PMI report, they later recovered ground, led by tech stocks, including Cisco Systems, which gained 1.9 percent to $23.75.
"It's end-of-the-quarter rebalancing," said Keith Springer, president of Capital Financial Advisory Service in San Francisco. "We saw some sell-off in the morning and now fund managers are buying into sectors that outperformed in the quarter, and that includes tech and financials, especially."
The Dow Jones industrial average rose 8.09 points, or 0.08 percent, to 9,750.29. But the Standard & Poor's 500 Index inched down just 0.17 of a point, or 0.02 percent to 1,060.44. The Nasdaq Composite Index gained 6.58 points, or 0.31 percent, to 2,130.62.
Commodities were also strong performers. November crude futures surged 4.6 percent to $69.79 per barrel after a government report showed an unexpected and large slide in gasoline inventories that helped boost RBOB gasoline futures.
Holly Corp gained 3.7 percent to $26.07 while Freeport McMoRan Copper & Gold added 1.8 percent to $69.54 on rising gold prices.
Late Tuesday, Darden Restaurants warned that its full-year same-store sales could fall more than expected, sending it stock down 6.8 percent to $33.71.
In other data on Wednesday, the ADP National Employment Report showed that private-sector job cuts were greater than expected in September, while the U.S. Commerce Department's final reading on gross domestic product for the second quarter showed GDP fell at a 0.7 percent annual rate, narrower than the 1.2 percent expectation.
The S&P 500 is up 15.3 percent for the third quarter, which ends Wednesday. For 2009, the S&P is up 17.5 percent and from a 12-year closing low in early March, it's up about 57 percent. (Additional reporting by Angela Moon; Editing by Jan Paschal)