President Obama may have downsized the number of official inaugural balls, but everybody knows that the real party goes on at the more than 100 unofficial galas and late-night parties, often sponsored by corporations, interest groups and state societies. 

These celebrations, some of which command $250,000 sponsorships, are an ideal environment for special interests and government officials to build relationships. Corporate executives — many of whom will be lobbying the new administration and Congress on a host of issues — will be gladhanding lawmakers while unions and associations fly in their stateside members to do the same. 

State soirees

One of the most well-known events is the Texas Black Tie & Boots Ball, held at a resort and convention center about 10 miles south of the U.S. Capitol. Members of the Texas delegration, from Dallas Democrat Eddie Bernice Johnson to her Republican House colleague Pete Olson of Sugarland, are expected to attend. Blue Cross Blue Shield of Texas, part of a coalition of healthcare companies seeking changes to the individual mandate in the new health care law that takes effect in 2014, is the top sponsor of the event, shelling out $250,000. The sponsors paying $50,000 each include Exxon Mobil, Chevron, Southwest Airlines and United, according to Veronica Custer, the ball's communications director. A full list of sponsors is posted on the group's website. You can check out their campaign contributions and lobbying expenditures on Sunlight's Influence Explorer.

At the gala held by the New York, Maryland and Delaware State Societies, featuring members of Congress from those states, a sponsorship is not quite as expensive. Fluor, the engineering and construction company with huge government contracts, is shelling out $25,000 to be the top sponsor. The company was awarded to head the reconstruction of the transportation hub underneath the former World Trade Center, which was completed in 2011. New York State Society's vice president of membership, Beverly Frey, wrote in an email that she was not comfortable naming the other sponsors of the event, which will take place Sunday evening at the Fairmont Hotel.

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MORE: Sunlight's Political Party Time maps the inaugural weekend fetes.

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Meanwhile, Georgia is honoring the President with an Inaugural Gala featuring hometown favorites Gladys Knight and Atlanta Braves legend Hank Aaron. Currently the only sponsor at the $100,000 “Diamond” level is insurance giant Aflac, which was founded in Columbus, Ga. in 1955. Coca-Cola, also founded in the Peach state, is contributing $50,000, while companies like Kia, Home Depot and UPS are donating $25,000 to the event. Notably, the American Peanut Shellers Association is chipping in $10,000 — perhaps to make amends for the bad rap President Jimmy Carter gave its crop during his subdued inaugural celebration.

The biggest sponsor at blue collar Pennsylvania's gala is a labor union — the International Union of Painters and Allied Trades at $50,000. Other big sponsors for the event, which is headlined by Queen Latifah, include Comcast and Chevron — at $25,000 apiece — and the International Brotherhood of Electrical Workers at $15,000.

The IBEW is also a big sponsor (New Jersey Seashore level) of the Garden State Inaugural Gala, along with various big-name representatives of the what-exit state's favorite industries: financial services and big pharma. The evening's attractions include an "Atlantic City Boardwalk Casino," sponsored by the American Beverage Association, and a New Jersey Diner, brought to you by Winning Strategies Washington, a lobbying outfit whose partners include Michael Merola, a former deputy chief of staff to ex-Sen. Bob Torricelli, D-N.J., and Donna Mullins, a former chief of staff to ex-Rep. Rodney Frelinghuysen, R-N.J.  Organizers of the gala are also urging guests to contribute to the "official charity" — the Hurricane Sandy New Jersey Relief Fund.

Interest groups imbibe

Interest groups are also putting on lavish events and attracting corporate benefactors. The environmental lobby — led by the National Wildlife Federation — landed Will.I.Am and Camp Freddy to perform at its Green Inaugural Ball at the Newseum, with Obama cabinet members such as Energy Secretary Steven Chu and Sens. Tammy Baldwin, D-Wis., and Tom Udall, D-N.M., on hand. By contributing $60,000, the NWA is the event's top sponsor but Wal-Mart, Honda, LG and Bosch all are chipping in $10,000. 

Where politics and business collide, lobbying powerhouse AT&T is often around. This time, the telecom company is the underwriting sponsor at "Out for Equality," the party featuring singer Frenchie Davis put on by Human Rights Campaign, an LGBT rights group. Other major underwriters are Verizon, Electronic Entertainment and Marriott — whose chief executive was a million dollar donor to a super PAC supporting Mitt Romney's presidential run. HRC did not immediately say how much the sponsorships cost. 

Naturally, one of the best parties in town is expected to be the one put on by the arts community: The Creative Coalition's star-studded ball, which raises money for the charity that has hired some top-gun lobbyists in the past, features a performance by the Goo Goo Dolls. A whopping 102 current and former members of Congress — including House Speaker John Boehner, R-Ohio, and Senate Majority Leader Harry Reid, D-Nev. — are expected to attend, according to Creative Coalition CEO Robin Bronk. But it's unclear who the sponsors are.

"That gets public when we report it to the I.R.S.," Bronk said. She added that none of the sponsors have asked for branding benefits, just tickets (a $100,000 sponsor gets you 50 VIP tickets). She called the event "truly selfless support of the arts."

Meanwhile Google is teaming up with liberal think tank Center for American Progress and Elle Magazine to put on a "Leading Women in Washington" brunch. The special guest list and entertainment is still in the works, CAP spokesperson Katie Peters wrote in an email. But the New York Times is reporting that a number of this year's record class of women members of Congress are expected to attend. 

Inquiring minds want to know

Three big-city Democratic mayors, Chicago's Rahm Emanuel and Los Angeles's Antonio Villaraigosa along with Philadelphia's Michael Nutter, are hosting two late-night soirees after the inaugural. Emanuel's event will include officials of the Obama for America campaign committee, which reportedly is about to morph into the Democratic version of Crossroads GPS. If you're one of the lucky ones who got an invite, we'd love a pic of the list of corporate sponsors. They're usually prominently displayed at the door — or by the bar. Email those photos to Sunlight's Political Party Time!