Wikimedia Commons and its fellow sites are hosted by the Wikimedia Foundation, a non-profit organisation based in the United States. Sites like Google or Yahoo are hosted on thousands of servers, with thousands of employees; we have around 800 servers and ~280 staff, and cover our costs through donations—almost all from members of the public.
If you're interested in donating to Wikimedia, you can do so here. If you've got questions about where your money goes, what we spend it on or what our plans are for the future, you can find out here. Should you have any problems donating, or other questions, please email firstname.lastname@example.org .