Apple, Google and Research in Motion have now secured about an equal amount of market share in the smartphone market, according to a new report from Nielsen.

Apple still leads the pack, but only barely, with 28 percent of all smartphone owners using an iPhone. 27 percent of all smartphone users have devices running Google’s mobile operating system Android, and the other 27 percent use BlackBerries.

But Google has a clear lead in terms of activations in December last year. 43 percent of all new smartphone users went with devices running Android. Google said that around 300,000 new devices running Android’s mobile operating system are activated each day — up from 200,000 devices in August. Compare that to the same month in 2009, when 13 percent of all new smartphones activated were Android phones.

Fewer new smartphone users have gone with Research in Motion and Apple’s products. 26 percent of new smartphone owners went with an iPhone in December last year. Research in Motion came in third with 20 percent of all new devices activated in December. In December 2009, 35 percent of all new smartphones were BlackBerrys and 31 percent were iPhones, according to the report.

It looks like Google’s mobile operating system has all the momentum behind it for the time being with the next version of Android, the tablet-optimized Honeycomb, due out soon. But new versions of Research in Motion’s BlackBerry surfaced on the web recently — including an iPhone-like Storm 3 and a new form factor that promises to hit a sweet spot for some BlackBerry users.

Research in Motion is also seeing a slight resurgence despite fighting a somewhat quiet battle with Apple for dominance in the enterprise space. While Research in Motion has around 55 million users, many of whom are enterprise customers, Apple has been steadily marching forward and increasing its presence in Fortune 100 companies. Research in Motion’s market share of smartphone users ticked up slightly between November and December and has since held steady in terms of new activations as of September.

The iPhone will hit the shelves for Verizon users this month and sales expectations are pretty high. The iPhone 5 is also just around the corner, as Apple has traditionally announced the next version of its iPhone over the summer. With each of the big 3 smartphone manufacturers releasing refreshed versions of operating systems and hardware, odds are the standings won’t change all that much unless one of them disappoints.