The Southern Poverty Law Center (SPLC) has published a report titled "Rage on the Right" that gives facts and figures on the resurgence of right-wing extremism in the US. It refers to an "an explosion of new extremist groups and activism across the nation" and notes that there has been a surge in anti-immigrant groups - an 80% increase, with some 136 new groups appearing in 2009.
Chip Berlet, a veteran analyst of the American right has this to say about the current state-of-affairs:

“We are in the midst of one of the most significant right-wing populist rebellions in United States history. We see around us a series of overlapping social and political movements populated by people [who are] angry, resentful, and full of anxiety. They are raging against the machinery of the federal bureaucracy and liberal government programs and policies including health care, reform of immigration and labor laws, abortion, and gay marriage."

The SPLC report gives examples of hard line positions on the American right:

The signs of growing radicalization are everywhere. Armed men have come to Obama speeches bearing signs suggesting that the "tree of liberty" needs to be "watered" with "the blood of tyrants." The Conservative Political Action Conference held this February was co-sponsored by groups like the John Birch Society, which believes President Eisenhower was a Communist agent, and Oath Keepers, a Patriot outfit formed last year that suggests, in thinly veiled language, that the government has secret plans to declare martial law and intern patriotic Americans in concentration camps. Politicians pandering to the antigovernment right in 37 states have introduced "Tenth Amendment Resolutions," based on the constitutional provision keeping all powers not explicitly given to the federal government with the states.

Hate groups in America have shown a steady increase - rising 54% between 2000 and 2008. So-called "nativist extremist" groups that go beyond advocacy to actually confronting and harassing suspected immigrants surged from 173 groups in 2008 to 309 in 2009. Militias and the larger Patriot movement that views the federal government as the enemy has also seen a dramatic resurgence. In 2009 some 363 new Patriot groups appeared.

Many are convinced that Obama's initiatives are socialist, even fascist. Their anxieties are fueled by on-air conspiracy theorists such as Glenn Beck who uses his propaganda clinic on Fox News to sow fear and create a fortress mentality. From the standpoint of America's greater good all this rampant negativity and fear mongering is self-defeating, but try telling that to people in the grip of irrational convictions.

There has been a revival of so-called "patriot groups" that the SPLC report describes as "...militias and other organizations that see the federal government as part of a plot to impose “one-world government” on liberty-loving Americans..."

Some of the rage has its roots in racism, even though the suggestion is adamantly denied by white folk who ironically enough vent against racial changes in American demographics and rail against immigrants. Yeah the changing face of America must be scary as hell for an angry minority who look at their country, their very identity, through racial lenses. But don't call them racist, they're just patriotic.

The report notes that in its heyday in the 1990's the Patriot movement was responsible for enormous amounts of violence, most dramatically the Oklahoma City bombing. It warns that the threat level is growing in the current climate:

Already there are signs of similar violence emanating from the radical right. Since the installation of Barack Obama, right-wing extremists have murdered six law enforcement officers. Racist skinheads and others have been arrested in alleged plots to assassinate the nation’s first black president. One man from Brockton, Mass. — who told police he had learned on white supremacist websites that a genocide was under way against whites — is charged with murdering two black people and planning to kill as many Jews as possible on the day after Obama’s inauguration. Most recently, a rash of individuals with antigovernment, survivalist or racist views have been arrested in a series of bomb cases.

Last year also experienced levels of cross-pollination between different sectors of the radical right not seen in years. Nativist activists increasingly adopted the ideas of the Patriots; racist rants against Obama and others coursed through the Patriot movement; and conspiracy theories involving the government appeared in all kinds of right-wing venues. A good example is the upcoming Second Amendment March in Washington, D.C. The website promoting the march is topped by a picture of a colonial militiaman, and key supporters include Larry Pratt, a long-time militia enthusiast with connections to white supremacists, and Richard Mack, a conspiracy-mongering former sheriff associated with the Patriot group Oath Keepers.

The date of the march is April 19. The report notes that this is the date when the first shots were fired in the Revolutionary War. It is also the anniversary of the end of the government siege in Waco and the 1995 Oklahoma City bombing.