Retailers last year began to flock in numbers to mobile commerce, a sales and marketing channel that’s finally coming into its own. According to a new report from Forrester Research Inc., this year stands to be a banner year for mobile retailing.

52.4% of U.S. online retailers are investing in mobile-optimized sites; a year ago that figure was just 18.6%, says the 2011 Online Retail Technology Investment Outlook. M-commerce sites give retailers greater reach than mobile apps because any mobile device with a mobile web browser can access a site; apps are built for specific smartphone operating systems and are thus limited in their reach.

44.4% of U.S. web retailers are investing in mobile apps; a year ago that figure was only 15.1%, the Forrester report says. While mobile apps don’t have the reach of m-commerce sites, they can provide richer, faster experiences that use the various features of a smartphone, such as data caching and GPS. Many m-commerce experts believe apps can draw retailers’ most loyal customers, who are more likely to keep an app on deck, or the mobile desktop.

When it comes to moving beyond investing and projects, a great many retailers plan to be in on the action this year. 47% of U.S. Internet retailers plan to have a mobile commerce site or app in place within 12 months, the Forrester report says.

2011 figures in the report are based on a sampling of 63 U.S. online retailers. 2010 figures are based on a sampling of 291 U.S. web retailers.