If some of you are motivated by xPL projects, I putted my work on github.
There is an example of temperature sensor working.
It's better for now to try it on an arduino mega / W5100.
You still can try it on a Uno/Enc28j60 but you'll need to upgrade avr gcc to 4.7.2
http://www.mgth.fr/drupal/?q=node/31
be warned that it is still at very, very early stage. I still have to deal with memory/flash usage to have the Uno version truly usable.