Research In Motion on Thursday announced a new promotion that will make its BlackBerry PlayBook tablet available to enterprise customers for free. Businesses that upgrade to RIM’s BlackBerry Enterprise Server (BES) v5.0 between now and December 31st will receive a free 16GB BlackBerry PlayBook tablet along with their purchase. Additional incentives provide up to $400 off installation services through participating partners. Earlier this week, RIM announced a sale that makes the PlayBook tablet available to consumers for $300 below standard retail pricing. Sales of RIM’s debut tablet have been lackluster at best, with shipments into retail channels totaling 500,000 units during the PlayBook’s first quarter of availability and just 200,000 units last quarter. As interest in RIM’s tablet tapers, sales of its latest smartphones stall and the company continues to burn through cash at an alarming rate, price drops and promotions appear to make up much of RIM’s strategy as it continues to tread water until the first round of BBX phones is ready to launch.