Much of my time is spent learning how LibreOffice Calc works. I definitely spend a lot more time doing activities such as reading code, understanding the code's intent, and analyzing the flow of code than I do actually writing code myself. This learning experience can be both enjoyable and frustrating... sometimes both at the same time. Even so, like I have said before on IRC, Kohei and Markus are the ones with the master plan; I'm just doing the grunt work. ;-)
On top of getting more experience with coding (C++) and analysis, I have also had the opportunity get familiar with some very useful development tools such as Git, GDB, Callgrind, OpenGrok, and Doxygen. Markus has also encouraged me to write unit tests for any feature that I touch that isn't already covered by a test and to improve tests that already exist. I have seen first hand several times how useful it is to have the unit tests catch features that one might accidentally break after modifying code.