Sons of Anarchy/WMG

Jax Teller is really Jax Morrow
In Season 1 Gemma burns an old photo of Gemma, Piney, John and Clay with a very pregnant Gemma in her wedding dress and in her husband John's embrace. Everyone in the photo is looking at the camera except Clay, who is looking at Gemma. In Season 2 Gemma suggests John subconsciously intended to cause the accident that took his life for reasons of unspecified pathos.

Speculation? Clay and Gemma had been having a relationship on the side for some time after Gemma became John's 'Old Lady', possibly even being the true sire of one or both of Gemma's sons. John found out about this and in anguish aimed his Harley at the front grill of an oncoming semi.
 * Unlikely, since Jax and his brother were born with the same heart defect as Abel, and Gemma calls it the "Teller family curse," suggesting that it was in JT's blood and not hers. She could have been lying about that, I guess, but why?
 * I'm pretty sure she just says "the family flaw," and she has a heart surgery scar on her chest, which suggests strongly to me that it was from her.

The Hamlet parallels.
Start with the obvious -- Jax, Clay and Gemma are Hamlet, Claudius and Gertrude, and Daddy Teller's book is the ghost. Moving on from there...
 * Horatio -- Tara
 * Polonius -- Piney
 * Ophelia -- Opie
 * Laertes -- Possibly Opie again.
 * Rosencrantz and Guildenstern -- I'm betting Bobby, and possibly Chibs or Juice.
 * Fortinbras -- Hale. The Nords may look like Norway, but Hale's the guy who's going to inherit Charming when the Sons are all dead.

Kozik is gay/used to be Tig's boyfriend.
The rivalry between Tig and Kozik ultimately played out in season three as if the two were ex-lovers, as seen by Tig's refusal to allow Kozik to transfer to SAMCRO Charming and the reveal at the end of the season that the reason for Tig's hate for Kozik stems from the as of yet stated fate of a dog that both men loved.

Kozik is gay and at some point in time (possibly after Tig was divorced from his wife) entered into a sexual relationship with Tig. The dog was something Tig purchased after his divorce and he saw it as a replacement for his daughters, who he may have been denied access to after the divorce. Kozik in turn also saw the dog as a surrogate child, in the way that many gay couples treat their pets as their surrogate children since they can not have children on their own. But the relationship fell apart, most likely because Tig isn't exclusively gay whereas Kozik is exclusively homosexual. And in the midst of the break-up, something happened to the dog while it was in Kozik's company.

It also explains why Kozik is constantly trying to start a fight with Tig/violence prone: as a gay man in the insanely masculine world of outlaw bikers, Kozik feels he has to be quick to violence in order to ensure no one thinks of him as a sissy incapable of holding his own due to his homosexuality. Tig might have also made homophobic remarks to Kozik, calling out his manhood due to him being gay and accused him of stalking Tig after the fact (which would explain the dialogue from Kozik's first appearance in terms of him getting into Tig's face).
 * This seems incredibly unlikely and actually a little ignorant to me. There's a lot of assertions about gay men/couples here that aren't true.

Season 4 will include a Time Skip and will open not long before the sons get out of prison.

 * The show has a fairly long production time between seasons, but in universe the time between seasons is fairly short(matter of weeks), and a given season rarely covers more than a couple months. Barely a full year(if that) has passed since the first episode in show. Season 4 will bridge that gap.
 * Confirmed. Season 4 picks up 14 months later with the cast getting out of jail, enough time for Abel to become a toddler and Tara to give birth and have a seven-month-old.

The Homeless Woman is an angel/ The Angel of Death

 * She appears at random times and places and always to push one member of the Teller family in a particularly destiny laden direction.
 * She showed up
 * She actually does say "Abel will help my boys." The second line "Able to help my boys," is a correction. That makes sense if one sees "her boys" as the members of the club.
 * Her original appearance comes just after at the same time as Donna and Opie's decision to take the family to Abel's coming home party.
 * Donna's appearance at the party led directly to which led to a number of other deaths throughout the series.
 * Her second appearance leads Gemma to the conclusion that she is meant to be a "fierce mother." This leads her to follow Polly Zobell which
 * Her most recent appearance
 * Her most recent appearance