Tinkerkit appears to be defunct, So you can find some of their stuff pretty cheap. Libraries are still on github.
So it appears these boards are much more then just LCDs - they have a 16x2 LCD of course, the firmware loaded on them let you use them as a serial LCD needing RX and TX hooked up to your micro-controller. But it turns out these have a Leonardo (like) controller on them, and are programmable via the Arduino IDE using the Leonardo setting.
I found some information on G+(I shared the link to the G+ community) that says the tinkerkit LCD is an Arduino Leonardo with a LCD screen, and has some information about the I/O on the board.
These boards can be found on eBay (From US sellers) for between $5.95 and $8 some offer free shipping, some don’t
And there are sellers wanting a lot more for these as well. Dan Moses says he finds them on Amazon for $8 bucks all the time (I haven’t looked, but seems right)
Special Thank you goes out to Dan Moses, as I have passed up a few of these boards thinking they were just LCDs.
So here is his blog that tells all about these:
He says he had a hard time finding the libraries, but a quick search of github and I found them no problem.
Dan Moses Codebender (Which he points too as the place to find the libraries) is:
I was only able to get these to program using Windows, and I selected “Leonardo” from the board list in the Arduino IDE. Dan says they are very picky about the USB cable, but I tried 15 or so on Linux, with no luck, same cables worked fine with Windows. I don’t know.