I'm currently reading the "Guerilla Home Recording" book that I recently bought. In the section on separation by panning, the author mentions "panning the reverb". For example, he suggests placing the vocal in the centre and the guitar to the left but the guitar reverb to the right. What does this mean? What does it do? Can it be done on Sonar?

This is a creative thing, what you are trying to do is put the instrument into a space.  So imagine your recording a real guitar with a real band.  The guitarist is on the right (on the mix you pan the guitar hard right), for instance so you use the buss panner and you pan the reverb hard right.  The reverb is in stereo but the bulk of the guitar verb is coming from the right, so when you listen back you feel like your in a room.

Somebody will explain it better than me, I know of the technique you are talking about and I can't remember why but I'm pretty sure it has something to do with space and creating the illusion of space.

Here this is not a guitar based song but it is a good example of panning reverbs and delays and it might help you understand the concept better: http://soundcloud.com/aaudiomystiks/yellowcandy

Peace Ben

Yes, you can do it in SONAR, and it can be very effective. Not for everything, but hard-panned guitar is one thing that it does work well for. 

IF you have a true stereo reverb plugin on the reverb bus (not all reverbs are true stereo, meaning they process left and right inputs independently and respect their pan positions) you can manage it via the Send Pan slider on the guitar track. You may have to disable the "Follow Track Pan" option, as when that's enabled the send automatically follows the main track pan slider.

If your reverb plugin is not a true stereo processor, you'll have to implement it with two separate reverb busses, one panned hard left and the other hard right. This isn't nearly as desirable, because you're probably sending other tracks to the reverb bus as well and you take away the reverb plugin's ability to spread reflections across the panorama.

OK fellers, I've got enough to go on there, I reckon. Thanks!

Listen to Van Halen's first album and you'll get the idea.

Van Halen?  Do I have to?