Non-profit organizations often seeking to influence members of Congress fund millions of dollars worth of free trips each year to "educate" lawmakers. You won't believe what one group paid for a lawmaker and his wife to travel earlier this year. (Jeff Simon/The Washington Post)

Sen. Ted Cruz (R-Tex.) is on his way to Estonia at the moment – the final stop in a weeklong four-country trip paid for in full by a conservative nonprofit group called Secure America Now. We don’t know how much the trip cost – but we will soon, thanks to congressional disclosure rules.

So far this Congress, nonprofits have funded 2,844 trips for lawmakers, including the most expensive such trip ever funded – a $49,635 trip to Australia for Rep. Mike McIntyre (D-N.C.) and his wife in February. That trip was paid for by Defence Teaming Centre Inc., an Australian defense industry nonprofit.

While American taxpayers don't pay for any of these trips, critics argue that lawmakers may be unduly influenced by the groups that do.

Thanks to Legistorm, which compiles disclosure records, we know a great deal about these trips – and the lawmakers who take them.

Want to know if your senator or representative has taken a free trip? Tweet us their names using #freetrips and we'll tell you.