Samsung this week released some of the source code that powers their recent NX-300 camera. That makes it probably the most high-level camera open to hackers (in the good, original sense of the word "hacker"). Working with this code is not a trivial task, and you'll need some familiarity with Linux, Tizen, ARM, Debian, and possibly even Webkit if you're really going to make substantive changes or additions to the camera firmware. The 10-step "build a package" instructions are in total geek, so beware. Moreover, it's not the complete set of code you'd need to change the camera's firmware.
Why is Samsung releasing the source code? Some of the components licensed in the firmware require that, as the Open Source projects they're based on contractually require disclosure.
If you're interested in taking the NX-300 hacking challenge, head on over to Samsung's open source site, click on the Photography tab, and download the TAR file (the NX-2000's software is also here). Beware: the TAR, despite compression, is over 6GB in size.