BitC (seems to be dead): http://www.bitc-lang.org/index.html
Habit (Haskell adapted for systems programming): http://hasp.cs.pdx.edu/
Apart from this family the other I have been window-shopping on is the high performance/productivity family, consisting of the likes X10, Chapel and Fortress. Thanks to Oracle, Fortress is now abandonware.
Off late I have been quite disappointed by this trend in HN to be very hostile to things that I would consider to be the very distinguishing traits of a Hacker. Now it seems some people here compete to jump over the other to complain against things that encourage/facilitate or are meant for tweaking, learning, exploring and breaking: all things that I consider the very essence of hacking. Case in point, recent discussion on Gentoo.
The behavior reminds me of a bunch of desperate and wannabe Pink Floyd fans we had in college, who would jump to rally the crowd to disco to the opening strains of Another Brick in the Wall, much to our bewilderment but apparently to look cool.
There is always Java, if you are happy with it, stay happy with it.
Felix is on my big list of interesting languages, but I didn't really think of it in the same category as these. I'm sort of aiming for something better than C when I get around to writing an OS kernel, you know, "someday".
I think for your use case decac, clay, bitC and Cyclone would indeed be ideal. There is this Haskell like language with effects based typesystem that might be worth looking at, the name continues to escape me.
One can go very low level with Felix, after all you can write inline C, C++ and define C and C++ functions, but those are not type checked. ABI could also be an issue given that it compiles to C++.
All the best for fun with kernel writing :)
Disciple ? (DDC)
Cyclone is pretty dead.
It's pretty incomplete, and definitely not ready for prime time yet.
I like to read about this stuff and compare design decisions between languages.
http://code.google.com/p/j-rest/ (meta: api creator)
https://code.google.com/p/szl/ (google data project)
http://luvit.io/ (nodejs for lua)
http://zenlang.sourceforge.net/index.html (in dev)
http://ufo.wikispaces.com/ (in dev)
http://code.google.com/p/penor-programming-language/ (a joke?)