PAC stands for Political Action Committee. PACs raise and spend money to elect and defeat political candidates, and most PACs represent special interests — business, labor, or ideological. PACs can contribute directly to political candidates. PACs can give $5000 to a candidate committee per election, $15,000 annually to any national party committee, and $5,000 a year to another PAC. The first PAC was the Congress of Industrial Organizations, formed in 1944 to raise money for the reelection of Franklin D. Roosevelt.
Source: OpenSecrets

Super PACs were created in July 2010 following the Supreme Court ruling in SpeechNow.org v. Federal Election Commission. Super PACs can raise and spend unlimited amounts of money to advocate for or against political candidates. They must report their donors to the FEC, and unlike PACs, they can't donate directly to a political candidate.
Source: OpenSecrets

A bundler is an individual who collects contributions from others and then directs money to a particular candidate. Many lobbyists are bundlers, and politicians are supposed to report lobbyists who have bundled money for their campaign to the FEC. However, politicians are not required to disclose funds bundled by individuals who are not registered lobbyists. It is currently estimated that at least $106,400,000 has been raised by bundlers to support the Obama re-election campaign.
Sources: The Hill and OpenSecrets

The revolving door is the flow of Congress members and their staffers that move into the influence peddling industry after the end of their public service career. A Public Citizen report found that 43% of Congress members that retired to pursue careers in the private sector went into lobbying. Similarly, a LegiStorm study found that in a period of 10 years 5,400 staffers joined the lobbying industry.
Source: Public Citizen and LegiStorm

K Street is a street in Northwest Washington D.C. where many lobbying firms have traditionally been located. Though many lobbying firms moved out of the area beginning in the late 1980s, "K Street" is still commonly used in mainstream discourse to represent Washington's lobbying industry.
Source: Wikipedia

On K Street and beyond, the number of active, registered lobbyists in Washington last year was 12,655. That's 23 lobbyists for every member of Congress. In 2007, the number of lobbyists was 14,840, the greatest it's been since 1998.
Source: OpenSecrets

On January 21, 2010, the Supreme Court of the United States rules 5-4 that corporations and unions have the right to spend unlimited amounts of money on political speech, such as advertisements, as long as they do so "independently." The decision, known as Citizens United v. the Federal Election Commission, cited the logic that more speech is better than less, and it is only acceptable to limit political speech (of which spending is a form) when it causes corruption. As long as spending isn't coordinated with a candidate's campaign, the Court held, it does not lead to corruption, so its limitation is unjustified. 80% of Americans oppose this decision.
Source: ABC News

"Citizens United decimated what remained of campaign-finance reform, but the damage has been long in the making." For more information on the impact of Citizens United and corporate personhood, read this article in The American Prospect by Garrett Epps.

Corporate personhood refers to the way U.S. law treats corporations as rights bearing persons in some circumstances, such as the ability to enter into contracts. The concept has been around for over a century, since the 1886 Supreme Court case of Santa Clara County v. Southern Pacific Railroad.
Source: United Republic

The presidential candidates in 2008 raised a combined $1.64 billion. Barack Obama raised $778,642,962 which works out to $10.94 per vote, while John McCain raised $383,913,834 or $5.97 a vote. For comparison, the combined amount of funds raised for the 1996 election was $448 million.
Source: Federal Election Commission

In the two years prior to taking office, our current Congress raised on average per member:

• Senate: $6,400,000, or $8700 per day
• House of Representatives: $1,200,000, or $1700 per day

Source: MapLight

It's estimated that members of Congress spend anywhere from 30 to 70% of their time fundraising. Much of these efforts are directed at lobbyists, since HLOGA disallows gifts from lobbyists but permits campaign contributions. The Sunlight Foundation found that nearly 25% of fundraisers happened over breakfast.
Sources: Republic, Lost, Lessig, Lawrence, p. 138; Sunlight Foundation

Yes, once a politician is elected he or she has an immense fundraising advantage. In the 2012 election cycle, House incumbents running for re-election outraised their challengers $405 million to $88 million, which works out to $972,014 per incumbent and $137,208 per challenger. In the Senate, the cash advantage is even more staggering. Senate incumbents raised $8,275,998 per candidate while their challengers were only able to raise $700,256 per candidate.
Source: OpenSecrets

No. There is no current requirement for members of Congress to disclose their meetings with lobbyists. New York Senator Kristen Gillibrand is the first Senator to fully disclose her meetings with lobbyists.

In 2011 private companies and special interest groups spent $3.32 billion lobbying their agendas. In 2010, they spent even more at $3.54 billion. 13.5% of the total money spent lobbying last year was by the finance, insurance, and real estate sector. From 2008 to 2010, 30 Fortune 500 companies spent more money on lobbying than they did on taxes.
Sources: OpenSecrets and ThinkProgress

HLOGA, enacted in 2007, says that members of Congress cannot accept gifts from lobbyists. That means a lobbyist can no longer take a Senator out to dinner. However, there's an easy way around it that's still legal; the Senator can pay for dinner and the lobbyist can make a campaign contribution. The number of fundraising parties of this nature likely has increased as a result of HLOGA being enacted.
Source:  New York Times

Senators now face a "cooling off" period of two years, so they must wait to start lobbying when they leave office. For one year after leaving employment, senior Senate staff cannot lobby with the entire Senate and senior House staff cannot lobby with their office or committee. Cabinet secretaries must wait two years before lobbying their department. These measures are only a temporary fix; as cited earlier, a Public Citizen report found that 43% of retired Congress members who went into the private sector became lobbyists.
Source: OpenCongress

In 2010, 27% of direct contributions to candidates were made by women, a 6.3% decrease from 2008. Women also made 21% of contributions to PACs in 2010. There has been a trend of declining donations from women from 2006-2010, which coincides with the first backslide in electing women to office in over 30 years.
Source: She Should Run

The top three female incumbents in 2008 raised $33 million — $16 million less than the total for the top three male incumbents.
Source: She Should Run

In the United States' current form of electoral politics, campaigns are funded by a combination of private and public money. Publicly funded elections refer to the act of funding campaigns from money within the government budget in an effort to curb the fundraising race that so consumes political candidates' attention and time. Methods of enacting public funding can range from the government matching the number of small donations a candidate receives to other kinds of government subsidies, such as providing television airtime at low rates to all candidates. The Fair Elections Now Act (introduced in the Senate and House of Representatives as S. 750 and H.R. 1404, respectively, in 2011) is a current example of how public financing could work. The passage of this act would enact a voluntary program for incumbents and their challengers to receive federally matched funds if they agree to limit their donations to small contributions under $100. Public financing proponents believe that publicly funded elections decrease corruption, increase civic participation, and force candidates to appeal to their constituents, rather than special interests and lobbyists.
Sources: Americans for Campaign Reform, Common Cause, Fair Elections Now, Public Campaign