The three "irresistible sirens of American politics," as drawn by Nick Anderson of the Houston Chronicle, are intimately related to (you can even argue that they're the by-product of) one thing: pork-barrel projects [wiki].
"Pork" projects, also often called "earmarks" in the federal budget, are provisions stuck in bills by members of Congress to direct federal money, without going through established budgetary procedures, to their districts.
Pork-barrel politics is anything but new: one of the earliest example of pork as the construction of highways introduced by John C. Calhoun [wiki] in 1817. Today, both Democrats and Republicans alike engage in pork-barrel politics.
Every year, the Citizens Against Government Waste, a taxpayer's watchdog organization, publishes The Congressional Pig Book detailing pork-barrel projects in the federal budget. According to the 2006 Pig Book:
This year’s list includes: $13,500,000 for the International Fund for Ireland, which helped finance the World Toilet Summit; $6,435,000 for wood utilization research; $1,000,000 for the Waterfree Urinal Conservation Initiative; and $500,000 for the Sparta Teapot Museum in Sparta, N.C.
This year, there was good news and bad news. For fiscal 2006, appropriators stuffed 9,963 projects into the 11 appropriations bills, a 29 percent decrease over last year’s total of 13,997. Despite the reduction in the number of earmarks, Congress porked out at record dollar levels with $29 billion in pork for 2006, or 6.2 percent more than last year’s total of $27.3 billion. In fact, the total cost of pork has increased by 29 percent since fiscal 2003. Total pork identified by CAGW since 1991 adds up to $241 billion.
Here's the 375 of the juiciest pork projects, summarized by the 2006 Pig Book: Link