Are there any free renderfarms available now that support the latest version of Yafray (0.8 ) via the Blender Yafray Plugin?
My computer only has 512 MB of ram and right now with this Yafray render it is swapping at 1.3GB. I have a feeling that constant swapping is not good for the disk.
Repeat after me “I_am_not_Linus_Torvalds”… just kidding 
Actually your question is a bit vague. By free renderfarm, you mean what?
Someone elses renderfarm that you can use for free? Not really. There is some group that is sharing time, like a seti at home kind of arrangement. (I forget what it’s called) But no free computers to use out there. 
I have been looking into setting up my own two extra boxen, for use as my own mini farm. If this is what you mean, then really your just looking to “set up” a render farm. Some render engines support clustering some do not. As far as I can tell Blender supports clustering via multiple thread usage and OpenMosix. Not a really good solution, but I am giving it a whirl to see if it can help. (it should have MPI support if you want good cluster support)
Basically OpenMosix is a loadbalancing cluster. OpenMosix will share threads (processes) to other nodes on the network based on who has the most cpu available to run that process.
MPI or message passing interface, is an API that allows a program that uses it, to actually run a single process through every node equally, thereby giving it that high computing ability that we all really want. (all linux supercomputer clusters that I know of use MPI).
Well… I am new at this blender thing too. So maybe there is an implementatin of LamMPI and someone who knows more will step up and tell us more about it.
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I am familiar with a one of the IT gurus at Boeing, they run linux on 120 node IA64 and Opteron systems doing laminar flow calculations that use MPI, and my brother set up the physics department system at WSU a 32node dual G5 setup that uses MPI. (ya, I wish I could get a little time on that puppyt to)
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http://renderplanet.com/ might help…
That seems like a nice place. It supports Blender and YafRay.
However, the prices are kind of high. I had the impression that they would have a super computer, like a Cray or something that could render thousands of times faster than the home PC.
I think I read something about a BURP (Big-Ugly-Render-Project) somewhere that was a share CPU cycles kinda thing, I don’t think it’s up and running yet but I haven’t checked in on it for a few months.
I have done some basic MPI programming before and it isnt that hard to do. Since blender is a big programme, it may be hard to MPI the code 
I agree though, MPI is probably the thing we would want to do!