Hi Per,

With a CAN bus bitrate below 250 Kbits/s you may use a simple hardware with only a protocol device (included or not in the microcontroller) and a driver (like PCA82C251). With 250 Kbits/s and up to 1Mbits/s you have to tune your line because you are in high frequency datalink. The use is that the bus line should have an impedance of 60 ohms. This can be easily done with hardware. I will add some schematics on my website which is comming soon. Note also that I'm experienced on the low level of CAN. There is a lot to take care according to EMC. I'm going to add all this on my website...

As I've worked a long time with CAN and RS485 especially in automotive application, I would say that the use of each bus isn't the same.
First, RS485 is usually a master/slave datalink whereas on CAN bus, each node sends its datas and from the other side, any node could read it...
Some advantages of CAN are that the datalink is faster, more reliable and many code sources and tools are existing to analyse and debug. Moreover, CAN bus is very flexible, easy to implement and when you've started with, you can use it to many projects only by changing a few things.
The disadvantage is that hardware is more expensive than RS485 and that the software for analysing and debugging may be also expensive if you plan to use only once. But if you plan to use it often, be sure that it becomes really interessting. Because these tools will help you to save time.... believe me !

In the past, The compagny where I was working was partner with KVASER in sweeden which designs and sells solutions for CAN busses for small costs. I know their products very well. You should check their website (www.kvaser.com). Their main competitor is VECTOR but their products are not better and are more expensive.

I could help you more if you precise your need.

Regards
Stephane