hdias:
But, I still do not have the Serial working with Uno and Mega2560.
Is your problem that you don't see the /dev/ttyACM0 in the arduino IDE?
I read somewhere in Gentoo forums or bugs, that the arduino-1.0 from portage has this problem for some people - So I decided to keep the old, "blue arduino" from the overlay for now.
But I can't find this thread again, sorry.