Well, since I'm in a good mood again, I'm going to start a new news series (across all three English-speaking calc forums) called "Highlights of the Month." Same deal as tifreaks "Projects of the Month," but I'm going to cover all three forums and won't cover everything, just the things I find noteworthy. Cross-posted projects get linked to the forum where the author appears to be most active (although if you are featured and would like a different forum linked, please PM me and I'll change the link). Ready? Go!

Monochrome z80
Ballrix z80 Assembly Remake by Xeda112358 - Xeda has remade DJ Omnimaga's Balltrix game for monochrome z80 calcs
Reuben Quest 3 by Sorunome - Sorunome has resumed work on continuing the DJ Omnimaga's Reuben Quest games with his own threequel
KnightOS by SirCmpwn - (8x color support as well) The third party OS for the 8x series has seen some improvements this month, as well as some improvements to the SDK and tools
TwoStep by DarkestEx/Muessigb - (Android support as well) Work has resumed on this puzzle game. The challenge: get from point A to point B under certain constraints. Is it hard? Yes

TI-84+ CE
LibLoad by MateoConLechuga - An appvar that allows for the use of dynamically linked libraries for the CE
Doors CE 9 by KermMartian - A CE version of Doors CS(E), with intentions of having full Hybrid Basic compatibility with Doors CSE
Alien Breed 5 Episode III by JamesV - (8x monochrome support as well) The third and final installment of the Alien Breed 5 port by JamesV, now with CE support (through an implementation of Mono2Color, originally designed by MateoConLechuga)
First Fantasy CE Port by DJ Omnimaga - A port of DJ Omnimaga's RPG of the same name (originally for the CSE)

TI-84+ CSE
Graph 3DC by KermMartian - A CSE 3D grapher with full OS integration

68k
X3D by catastropher - (PC support as well) A 3D engine for the 68k series (and PC) that has made a lot of progress this past month

HP
MinePrime by alexgt - A 2D Minecraft port for the HP Prime. Similar to Jens_K's Nspire Lua version

PC
CEmu by MateoConLechuga - It kind of goes without saying, but this CE emulator is the biggest news of the month from December. Progress has been steady this month, with file transfer, new keyboard layouts, and other features being added
TI-84+ CE C SDK by MateoConLechuga - Once again, probably the biggest news of the month, but of January, not December. A fully-functional C SDK for PC for the CE that allows for easier programming for us non-assembly folk

Oh, I completely forgot about Balltrix @_@ I may have actually made updates, but I'll have to check later.