This is very useful: Propublica is compiling a complete, searchable list of all the last-minute regulations the Bush administration is trying to jam through before Obama takes office. It's hours of fun, if you're into that sort of thing, though three rules in particular are worth a closer look here—two on factory farms, and one on mountaintop mining.
First, the farms: I hadn't seen any mention of this newly finalized EPA rule that would essentially allow "more than 15,000 factory farms across the country to avoid certain requirements of the Clean Water Act if they claim they do not discharge animal wastes into lakes, rivers and streams." Here's a short article on the new rule from ENS, which notes that concentrated animal feeding operations (CAFOs) produce some 500 million tons of cattle and poultry waste each year—usually storing it in massive open-air lagoons or dumping it on land, where the waste can contaminate local water supplies. In 2005, the courts ruled that there was no good way to hold CAFOs accountable for polluting the water under this system, so, in response, the EPA created this updated regulation, which… doesn't even explain what would happen to factory farms that refuse to get permits and fail to meet clean-water standards. It's quite the honor system.
Of course, as many environmentalists will note, the gravest health risks from CAFOs, what with all those cows and pigs and chickens crammed together in a tight space, often come from the air pollution they produce, rather than water pollution: One Wellesley professor, Stacy Sneeringer, recently found that the presence of factory farms can significantly increase infant mortality rates in a county—possibly due to all the ammonia and hydrogen sulfide emitted by the concentrated feedlots. Lucky for us, though, the Bush administration has a new rule on this, too. Let's see... yep, the new proposal would largely weaken existing protections by exempting farms from reporting their animal-waste air pollution, so long as they keep any hazardous releases below a certain threshold over a 24-hour period. True, this makes it a lot tougher to figure out whether farm air pollution is making the locals ill, as is sometimes the case, but the livestock lobby is thrilled, so that's that.
Also still under review, I see, is a new Interior Department rule that would make it much more convenient for mining companies to dump their debris into waterways when doing mountaintop removal (in which they blow off the tops of mountains to get the coal buried underneath). The administration's reasoning was that mining companies pretty much ignore the existing ban on debris dumping anyway, having wiped out some 1,600 miles of streams in Appalachia since the mid-1980s, so why not just formalize the process? They don't seem to have considered that they could also just enforce the laws already on the books...
Update: The mining rule change just got final approval from the EPA (this despite the fact that the agency has consistently deemed the existing stream-buffer rule necessary to preserve downstream water quality).