The foundation somewhere has an overview of what is spent where.
There was/is (not sure, if it was closed since the foundation was created) an account that was directly managed by the team.
Since I am not directly involved in that part, I do not keep track of all the things...
Some money goes into the infra structure. IIRC in the past some money was used to buy a MacBook for one of the developers, to enable more Mac related development.
You can also purpose your money directly to specific causes, for example by setting bounties on the wiki. Either something you need, or features you know to be missing but wanted by others, or bugs from mantis....
Or speak to the foundation if they be willing to support some feature...