Time, money, and what the boss wants can limit what you learn in a given year. If you could choose, what development technology would you learn in 2010?
While I did not have the chance to learn many of the things I intended to learn this year, I certainly tried. For next year, I would definitely like to learn more about the new .NET 3.X and 4 technologies (I still know nearly nothing about WPF, WCF, and Workflow Foundation) and possibly learn F# in depth.
Some developers don't have much choice about what to learn — they have to focus on whatever their workplace needs them to learn. Tell us what's on your agenda to learn next year.