Open source, Apple computers, green technology, the rise of users and the proliferation of three-dimensional printing are among the hot trends IT shops should look out for in the next few years, according to Gartner.  (Fellow industry watcher Forrester Research also issued predictions this week.)

The analyst firm on Thursday highlighted 10 key predictions of developments that will affect IT and business users in 2008 and beyond. Here’s a detailed look at the list, culled from more than 100 predictions Gartner has made based on its research:

*Apple will double its market share for computers in the United States and Western Europe by 2011. “Apple’s gains in computer market share reflect as much on the failures of the rest of the industry as on Apple’s success,” Gartner says. A focus on interoperability between the iPod, iMac and other devices is one of the keys for Apple.

*By 2012, half of all workers will use devices other than their laptops when they travel. “Even though notebooks continue to shrink in size and weight, traveling workers lament the weight and inconvenience of carrying them on their trips,” Gartner states. “Vendors are developing solutions to address these concerns: new classes of Internet-centric pocketable devices at the sub-$400 level; and server and Web-based applications that can be accessed from anywhere.”

*80% of commercial software will contain open source code by 2012, providing “significant opportunities for vendors and users to lower their total cost of ownership and increase returns on investment.”

*Software-as-a-service will account for at least one-third of business application spending by 2012. “Endorsed and promoted by all leading business applications vendors (Oracle, SAP, Microsoft) and many Web technology leaders (Google, Amazon), the SaaS model of deployment and distribution of software services will enjoy steady growth in mainstream use during the next five years,” Gartner writes.

*IT infrastructure will follow the software-as-a-service wave, with early technology adopters purchasing 40% of their infrastructure as a service by 2011. “Increased high-speed bandwidth makes it practical to locate infrastructure at other sites and still receive the same response times,” Gartner notes.