DryShips Inc. (Nasdaq:DRYS), A Power Energy Generation Systems Ltd (Nasdaq:APWR) and Dendreon Corp. (Nasdaq:DNDN) are among the most actively traded companies in Friday's trading among companies with market capitalizations under $1 billion.

Also included among the results: Canadian Solar Inc. (Nasdaq:CSIQ), Pozen Inc. (Nasdaq:POZN), Clean Energy Fuels Corp. (Nasdaq:CLNE), American Superconductor Corp. (Nasdaq:AMSC), Aladdin Knowledge Systems Ltd (Nasdaq:ALDN) and ATP Oil & Gas Corporation (Nasdaq:ATPG).

Here are the most actively traded companies among small caps:

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