If you have an ADP/G1(root) you can easily put your phone into WiFi ad hoc mode. This is useful for a number reasons, not least because it allows you to easily connect to your laptop.
But although this is easily supported by the platform and the OS, it is not available in the GUI settings, nor in the SDK. This essentially locks out non rooted users and developers from using WiFi in ad hoc mode.
There is a patch available that provides this functionality, but it is not part of the android source tree, and Google is very silent about it.
I am interested in learning how many people that would be interested in using this, to develop applications, or just as a nice wireless communication link.
Please let me know if you are interested in this. It would also be interesting to learn what you would like to do with this functionality, if you had it.