As I mentioned here a few days ago, it looks like ETS is updating its TOEFL/IELTS concordance tables. For this reason, there is currently a sweet offer for test-takers based in the USA and Australia.
Individuals who have taken both the TOEFL and IELTS within the last six months (and within three months of each other) may be eligible to receive a $100 Amazon gift card after sharing their score reports.
Those who have taken the IELTS only may be eligible to receive a $100 gift card plus a voucher to take the TOEFL for free.
Note that all tests must be taken at a test center, not at home.
Details here for people in America. And here for people in Australia.