In the US, ‘pork barrel’ (or just ‘pork’) is a derogatory term applied to wasteful government spending – generally applied to spending that is intended to benefit only a particular representative’s district or senator’s state and thereby buy votes for that person.
The typical way it is done is to attach such projects to major bills, where they will presumably attract little attention (or they are attached by the leadership in order to buy the beneficiary’s vote). The stimulus bill was laden with billions in pork projects and the immigration bill passed by the senate includes a provision declaring Nevada a border state (which will surprise most geographers) and spending a bunch of money on promoting travel to Las Vegas.
Here in the Philippines, the corruption is much more open. Here, each member of the congress is given an amount of money to spend in any way s/he pleases. This is openly referred to as his/her pork barrel (e.g., a paper will write “the project was paid for from Rep. Gomez’s pork barrel”). The proper name is the Priority Development Assistance Fund, but nobody calls it that.
The amounts involved are not trivial, considering the poverty of the country. Each senator gets two hundred million pesos annually (about $5mil), while each representative gets seventy million. Given that there are twenty-four senators and almost three hundred reps, this totals out to over twenty-five billion pesos, about 1.5% of the country’s budget.
You can buy a heck of a lot of votes here for P200mil, the going rate being I think P200/vote (and in a congressional district, P70mil goes even farther). Most is not used for outright vote-buying, however. I understand that the usual thing is to build something in the district, thus securing votes, and have it built by the politician's family construction company, thus pocketing the money. Sort of a two-fer.
If need be, of course, the profits from the project can be used to buy more votes at the next election, which allows you to hit the trifecta.
I don’t know if they have to report how the money is spent. There probably is some sort of pretense at reporting, but given how things are done here, I would expect any reporting to be very vague and limited, hidden from the public, not reported on by the press, and not audited in any way.