The most revealing episode so far has been 'The Red Barn':

1.- The detective 'Ray' whatever asks Theresa to leave CBI and join his soon to be private investigating team.

2.- He goes to Theresa and asks if the info from a certain guy helped them in the case...Theresa realizes nobody else knew about this...unless they had a connection with VISUALIZE. And so, she asks Ray how did he know about the info? He dodges with the usual 'someone in your team must of told me' crap. She continues pressuring him until he reveals he is part of VISUALIZE.

3.- He is not happy when he finds out the girl is only being charged for the murder of one guy and not the three, she presses Theresa to charge her for all three murders to which she obviously refuses.

Theresa asks him: 'Ray', if you joined VISUALIZE as a boy, then you were a member back in the 80's... Did you work in that farm back then?...'

He dodges the question right away...

So, based on that Jane found out during the episode...

A) Red John painted his signature face in the barn's outer wall, most likely after he killed the other two people and put them inside the basement.
B) Red John was a member of VISUALIZE back in the 80's...if not to this day
C) VISUALIZE is withholding information on membership lists from the 80's

So, if this Ray guy...

1) Is part of VISUALIZE
2) Was already part of VISUALIZE in the 80's
3) Shows an abnormal interest in this particular case
4) Refuses to answer Theresa's question of whether he worked at the farm during the 80's or not.
5) Knows information about the case that he shouldn't have known unless he knew it himself or was told through his VISUALIZE network.
6) Shows a keen interest in Theresa, even since the first episodes in which he appeared... coincidentally Red John is equally keen on Theresa when speaking to Jane...

Then, it is very likely he is either Red John or something VERY CLOSELY linked to him.

My current #1 theory is Red John is Detective Marco Francis.

He is played by the talented actor Brad Rowe, who incidentally, is the same age as Simon baker.

- He is very attractive, and resembles Simon Baker physically, has short straight hair and is about the same height as well.

- We've only seen him in a scene in the beginning of the episode 1x07 "Seeing Red". The original script, however, includes one more scene near the end of the episode where he tries to flirt with Lisbon (unsure why that was cut off from the episode).

- He lived in the same town as Kristina Frye, so that could explain a possible previous connection between the two.

- Being a detective, he is likely to be connected with other law enforcement officers both in the CBI and FBI.

- He is "Mar..."

- According to episode 5x13, even though Jane extended the age frame to 30s, I imagine Red John to be actually "kid", a teenager at the time he started killing, much like Rae Haffner, probably a disciple of Brett Stiles and Brad Rowe certainly fits that time range.

- I find it a bit strange that this particular actor only has a few lines in one scene in such a pivotal episode. Brad Rowe is usually more prominent as a guest star in other tv shows, and from what I've seen of his work, he is really good at playing innocent / evil guy. From a casting perspective, it's kinda odd that he played such an insignificant part and was never seen again. I can't help feeling Bruno Heller is hiding this guy as much as possible because once he makes another appearance, it will be evident he was Red John all along.

Hi fans.

The fact is, only Bruno Heller knows who Red John is. The director always confuses us and he previously mentioned: "everybody will try to find out who is the mysterious serial murder, but when Red John be reveal, the audience will be very disappointed"

Also fact is, Patrick Jane isn't Red John.

I tried to figure out who Red John is, but there are a lot of red herrings in the series, therefore I gave up. Also fact is, Patrick Jane isn't Red John.

Unfortunately, we have to wait, but I hope, in this season, finally we will see the unmask Red John.

I don't know if this has already been linked on this forum, but here is Owain Yeoman talking to John Troy Donovan (Ron) on set. I'm putting it up since it seems some people might like to see it.

Yes, you hear Donovan's voice.  And yes, Yeoman directly asks him: "Is Ron Red John?"

http://www.youtube.com/watch?v=0llrwyH08Sg&NR=1&feature=endscreen

Do with this whatever you will.  (Note: I'm not a big fan of the theory of Ron being Red John, but you never know.)