So my answer to the who should Sam be with discussion is. . .no one. It is rare, I think, that a person can go through life without being attracted at least once to an unobtainable person. Be they already involved with someone else, married, a ranking officer in the same chain of command, etc.
Proximity and shared experiences play into this equation as well. In the case of Sam and Jack, they share a military background, and work closely on a top secret project that they can't even discuss with their closest confidantes. That is, if they were ever shown on Earth and off base often enough to establish or foster relationships with people outside of the SGC or the USAF. To both O'Neill and Carter, honor, duty and responsibility are more than just words or nebulous concepts. Neither of them would ever act on their feelings. It would simply be inappropriate in the military structure within which they chose to live. And they both realize the possible dangerous repercussions that a relationship between them would have to their careers and to the team.
Very slight spoiler for COTG:
*
*
*
*
*
As to Sam and Daniel. . .Sam met Daniel and one of her first impressions was of him in the arms of his adoring wife. As 'healer of the emotionally wounded', I think Sam sees herself more as a supportive friend to Daniel. Particularly considering what he has suffered in his search for Sha're. They too share a scientific background, but approach it from two different directions. Sam and Daniel seem to behave towards each other more as siblings than anything else. Respected equals who speak the same language.
Sam and Teal'c. Well. . .as it has been mentioned, we just haven't seen much interplay between these two. So what could I say?
Thanks for letting me run on a bit. Quite a bit.
Renee. . .