Organizations including corporations, nonprofits, labor unions and political action committees have given more than $167 million to super PACs, about 30 percent of the money donated to them, the most recent campaign finance reports filed with the Federal Election Commission show.

Contributions to super PACs have topped the half billion mark at more than $543 million, while they've spent about $424 million in the campaign so far.

The breakdown of money from organizational givers is as follows:

• Corporations including their PACs: $61 million
• Labor Unions and their affiliated PACs: $49 million
• Nonprofits and trade groups: $39 million
• Unaffiliated PACs: $18 million

While no company has donated as much as power donors Sheldon Adelson and Harold Simmons, corporate givers have made use of the looser rules that followed the Citizens United decision to fuel super PACs. But like those individuals who've written seven- and eight-figure checks to super PACs, the biggest corporate donations are driven by individual CEOs. Oxbow Carbon LLC and Huron Carbon LLC, a pair companies controlled by William Koch, a brother of Charles and David Koch but not a partner in their political activities, have given $5.25 million. His more famous siblings have said they will donate about $60 million to political causes this election.

Similarly, Harold Simmons' Contran Corporation has contributed more than $3 million, Harlan Crow's Crow Holdings gave $2.3 million and Robert T. Rowling's TRT Holdings has chipped in $2 million. Melaleuca Inc., a household and healthcare product company, has given $1 million to Restore Our Future, the super PAC that's supporting GOP presidential candidate Mitt Romney. The firm's CEO, Frank Vandersloot, has been a Republican donor in the past, but has been more generous in this election cycle. Although this one of the first times he has become a national level big bucks donor, he’s been described as the single most influential donor in Idaho, where he is based.

Many companies prefer to donate to tax exempt organizations where their donations can remain anonymous. For example, last year the insurance company Aetna contributed to the American Action Network, a 501c(4), social welfare organization that does not have to disclose its donors but can spend up to half of it’s resources on political activities. And the U.S. Chamber of Commerce, which has spent $28.8 million on indpependent expenditures, raises most of its funds from corporate donors.

Among labor unions, the National Education Association ($8.4 million) the Service Employees International Union ($7.6million) and the AFL-CIO ($6.3 million) are the largest donors to super PACs, with most of the money going to super PACS organized under their umbrella. 

Although labor groups were late to the super PAC game, they’ve quickly picked up speed, especially in spending on grassroots activity, which has long been their main forte. In addition to ad buys, labor super PACs have been helping smaller campaigns with more feet on the ground, staffing the campaigns and door to door canvassing. 

The NEA Advocacy Fund has at least $3 million cash in hand, putting it in a position to intervene in key House races. The teachers union super PAC has already spent $500,000 against Richard Tisei, the Republican challenger to  scandal-plagued Democratic incumbent Rep. John Tierney of Massachusetts. That's still less than the $1.5 million that the National Republican Congressional Committee has spent in opposition to Tierney. Workers Voice, the AFL-CIO affiliated super PAC has dabbled in several races, from the Presidential ones, where they have run ads against Republican presidential hopeful Mitt Romney to several close Senate and House races. SEIU's super PAC is been spending on the presidential campaign and House, Senate races. The committee has over $2 million in the bank at present.

Nonprofits with varying political leanings are the third largest group of donors to super PACs, including political nonprofits organized under section 527 of the Internal Revenue Code that don't report their activity to the Federal Election Commission. For example, the Republican Governor’s Association has donated about $5 million to their super PAC which has yet to make any significant ad buys and could be one to watch for in the next few weeks.

Other types of nonprofit groups, including social welfare organizations, have also contributed. American Bridge 21st Century, founded as a nonprofit to help the progressive movement, has it’s own super PAC to which it donates. The main advantage of having a nonprofit and an affiliated super PAC is that donors to the nonprofit remain unknown. George Soros, the liberal billionaire has so far been the groups’ biggest money man.

Native American tribes such as the Choctaw Nation that have long had a Washington presence are also donating to super PACs as well. These groups, which have lobbied on casino and gambling related topics, have given a total of about $325,000 to super PACs.