The recent uproar over ThinkProgress' claims against the US Chamber of Commerce is starting to turn up here here and there.
Here's their donation webpage. Note the International dropdown.
Note the disclaimer at the bottom:
Dues Deductibility:
Because the U.S. Chamber engages in lobbying, under federal law 50% of investments for 2010 is non-deductible; 50% is deductible.
The law clearly prohibits raising funds from foreign nationals for any election-connected vehicle (the Chamber's 501(c)(6) account is such a vehicle).
I'm half-tempted to encourage an international reader to make such a donation, a small one, and forward the receipt to ThinkProgress.org, as prima-facie evidence such donations are being made.