This isn't strictly speaking "this month", but more "since the last time this thread was around", perhaps three or four months. (ETA: actually, the last such I took part in was October '13.)

Built a 3D printer from a kit. Learnt enough G-Code and OpenScad to be dangerous. Designed a few parts of my own, including some that replaced original parts.

Lost about 6 kilos from my max weight. Anecdotally, what seems to have worked in my case was eating lots more vegs, liberal amounts of meat, and about half my previous quantity of carbs. Also increased exercise a fair bit, incorporating a lot more walking (to or near the oft recommended 10K steps a day) in addition to a weekly run (typically 10K). One of my major objectives was to not feel like I'd gone on a diet, but instead to rewire my preferences so that eating whatever I enjoyed would lead to weight loss. I worked quite a bit on identifying and removing the trivial inconveniences that were keeping me from enjoying vegs and salad more often.

Switched banks. Sounds easy when you write it like this but it's an insane amount of hassle.