I also like Rick and Michonne. That is why I am wary of Karen, I already have all the prison crew paired off in my mind.
Daryl and Carol (I hated Carol season 1 and 2 but she is awesome this season, and the writers have been slowly building these 2 up forever).
Rick and Michonne
Carl and Beth (in a few years)
Glenn and Maggie (obviously)
I was thinking that Karen could end up as an interest for Tyreese. But even if she ends up hooking up with no one (she may be dead by episode 2 of the next season, for all I know), her mere presence could light a fire under some of the other potential hook-ups and get them going!
For example, if Karen starts getting chummy with Rick, maybe Michonne will get annoyed and Rick will notice that annoyance.
If Karen sidles on over to Daryl and giggles at some of his witty one-liners, Carol might finally step up to the plate and get her man!
I don't like Carl, so I don't care who he ends up with!

As for Carol and Daryl - yes, there has been build-up and a kind of 'will they or won't they' tension for a while, but I'm not sure IF they will hook up. I don't picture Carol lasting too much longer on the show, for some reason. Sometimes they flirt (she flirts more with him than he does with her, I think) and sometimes there is more of a motherly vibe from her. Sometimes they just seem like unlikely pals. Let's face it - in the real world, that is a pairing that probably would not happen because they seem to be a mismatch. In the zombie world, people are forced together and end up bonding under bizarre circumstances and things may spring from that.
I heard an interview that Norman Reedus did last year at some point (with GeekTime on Sirius, I think it was??), well before season 3, and he was asked what was going to happen with Daryl and Carol. He said that he didn't know if they would end up together or not, but that IF they did he hoped it would -
and I am paraphrasing because I cannot recall the exact quote - not be a good experience. He didn't want it to be perfect and romantic and all of that. He wanted it to be flawed. It almost sounded as if Norman wanted a Daryl/Carol hook-up to be a disaster!
Then again, that was a while ago so Norman may have changed his mind since that interview!
The weird thing is, I never really saw any interest from Andrea towards Shane until....that moment in the car. I didn't think she was interested in Shane, nor he in her (well, we all know where Shane's heart was). But something was sparked when they were out shooting targets, and she suddenly looked at him differently. He, of course, was still hung up on Lori but an opportunity presented itself so he took it.
I think that if Carol just 'pulled an Andrea' and made an overt pass, Daryl might actually recoil and pull away
at first because he'd be embarrassed, or because he and Carol have become close friends and he'd be afraid of ruining that. And in some strange way he might not make a pass at Carol because he respects her and cares about her feelings.
So they'd have to get over themselves long enough to get anything done. They have to be put into a situation that gets them alone and away from the gang (like the Shane and Andrea set-up) so they can kind of see where things go, or see if things are not meant to go anywhere.