Grant,
I'm glad you brought this up, as it is a subject near and dear to my heart.

I'm using CAN in my projects and I love it. I use SILABS C8051F040. Among other things, it has a built in CAN controller that works great with little uC overhead. It works great, but it is a large leap to take from scratch. See the link for the BOSCH_CAN manual -
http://www2.silabs.com/public/do..._Guide.pdf
I had to read and re-read this thing umptean times before I could use it efectively, but I am using it effectively now. My project using this to date have all been 2-3 controllers with the same chip, OSC speed, and common software, so I have my own protocal for this, but I understands with a little (or maybe a lot) of work, it can be made to comply with devicenet or modbus protocals.

For Geert, If I was doing this, I would definitley use CAN, but only because I am familiar with the tools and chip and already ahve software for it (CAN communications). For your use, probably best to stick with what you already have (unless maybe your up for a challenge?)

Best regards
Andy