U.S. Geothermal Inc. (AMEX: HTM) leaped 22.73 percent to $1.35, on volume of 1,986,007 shares, or nearly 10 times its daily average. The Boise, Idaho company has scheduled a conference call for Tuesday, to discuss second-quarter financials. U.S. Geothermal Inc., a renewable energy company focused on the production of electricity from geothermal energy, owns and operates geothermal power plants at Raft River, Idaho and San Emidio, Nevada, and is developing the Neal Hot Springs project in Oregon.

Intelligent Systems Corporation (AMEX: INS) went skyward 50.93 percent to $1.60 in early afternoon trading Monday.  INS share volume surpassed 13,650 shares, dwarfing its three-month daily average of 1,267. INS, based in Norcross, Georgia, for 30 years, has identified, created, operated and grown early stage technology companies.

SPDR S&P 500 (NYSEArca: SPY) led AMEX volume stocks early Monday afternoon by trading in 81,826,044 shares. Daily three-month average is 194,042,000 shares. The index-based issue lost some traction, though, faltering in price 0.18 percent to $122.50.

Digital Power Corporation (AMEX: DPW) gave back 11.28 percent in price in early afternoon trading Monday to $1.73. Volume quadrupled its three-month daily average at124,392 shares. The company, based in Fremont, Calif., last week reported third-quarter revenues increased by 87 percent to $3,186,000, compared to $1,708,000 for the quarter ended September 30, 2009. Net income was $303,000 for the quarter ended September 30, 2010, compared to a net loss of $205,000 for the same quarter last year.