I got mine for AU$4.87 via eBay.
Sample software to drive it comes from the manufacturer Elechouse, here.
The board will transmit from 58MHz to 134MHz. It seems to get a little unreliable at the edges, I guess a PLL isn't locking or something.
I had to slightly modify the library for it to compile on the latest Arduino IDE. It seems they'd defined some integer sizes that are already defined these days.
In the file FMTX.h, up the top add this line:
#define __TYPE_REDEFINE 1
This will stop the type defines from being processed. Here's my test code based on their example.
float fm_freq = 134; // Here set the frequency
Anyway, a bit of fun for $5 and it certainly puts out a decent signal on the FM broadcast band. Disappointed I couldn't have a QSO on a ham band with it.