It’s safe to say that 2011 was a milestone year for Big Blue. The company churned out some significant advancements during the pas 12 months, and managed to make gains in a number of areas. One of them was the appointment of a new head, choosing of Virginia Romett as the successor of previous CEO Sam Palmisano.

The hunt lasted for years and included several other candidates, including Steve Mills, IBM’s software chief. In the end, Romett’s resume prevailed thanks to the major contributions she made during the time she’s served in various roles for the company.

Three rather recent studies by the tech firm have also made it into this yearly roundup. As microprocessors are getting smaller and smaller IBM has been looking into possible alternatives to silicon, and has found three. Among them is the first ever nanotube transistor, coming in at less than 10 nanometers.

Big Blue also made some plans for the short term, adopting a organization-wide BYOD policy.  In 2012 a total of 200,000 employees will be able to bring their own smartphones to work, thanks to a line-up of new and still in development products that this initiative will help to demo.

Another segment where IBM has grown immensely in 2011 is the whole topic of smarter – and greener – cities. One of its biggest projects announced this year was EcoGrid, a joint initiative between Big Blue and the EU that will leverage the cloud and connected devices to encourage the consumption of energy produced from eco-friendly sources.

Also this year, we’ve learned that the tech giant is working on what will become the (two) most powerful supercomputer in the world. A 10-petaflop behemoth named Mira will come into life in the Argonne National Lab next year, and an even more powerful deployment will be found in the Lawrence Livermore Labs.