Aggressive promotions through its US wireless carrier helped push BlackBerry maker Research in Motion ahead Apple and the iPhone to take honors as the most popular smartphone maker during the first quarter of 2009.

During the three-month period ended March, RIM’s consumer smartphone market share increased 15 percent to nearly 50 percent of the smartphone market versus the prior quarter, according to market research firm NPD, who does similar research for various other electronics companies.

The rise was good enough unseat previous top-slot holder Apple, whose iPhone along with handsets manufactured by Palm saw their share of the market each decline by about 10 percent.

NPD attributed the shift largely to an aggressive “buy-one-get-one” promotion by Verizon Wireless that helped RIM’s BlackBerry Curve move past the iPhone to become the best-selling consumer smartphone in the U.S. in the first quarter.

Apple’s fall from top of the smartphone charts wasn’t a huge surprise. Apple said last month it shipped 3.79 million iPhones during the first calendar quarter of the year. By comparison, RIM sold a record 7.8 million BlackBerries — or more than double the number of iPhones — between December and the end of February.