Sif/Loki - Backed up by the Myths?
I'm a big fan of Sif/Loki because I think they had such awesome chemistry in the film and I find it difficult to think it was purely accidental. I'm happy to ship them completely on this and don't consider them anti-canon perse, just never directly mentioned in canon.
Anyway, since seeing the film, I've come across a few sources that hint, quite strongly, that Sif and Loki had a relationship in the myths - making them a lot more "canon".
My favourite piece of evidence is the Lokesanna quote, Poetic Edda, stanza 54. In this, Loki basically accuses Sif of having an affair with him. Loki to Sif -
"I alone know, as I think I do know, your love besides Thor, and that was the wicked Loki".
In the poem, Sif makes no comment on this at all, not even to deny it. Also, earlier in the poem, stanza 48, Odin (in disguise) tells Thor that Sif (Thor's wife in the myths) has a lover at home (Source).
My second favourite piece of evidence, is that Sif has a son called Ullr (or Uller) who is the stepson of Thor. The father is unknown, but he is most likely not an Aesir (the race of Asgard). According to Myths of the Norsemen, by Helene A. Guerber (orig. published in 1909), Uller loved the cold and his father is probably a Frost Giant (Source). Also, Ullr's latinised name, Ollerus, "is described as a cunning wizard with magical means of transportation" (Source). So a few hints here of who the daddy could be... (my guess is on Loki!).
Also, the whole Loki cutting Sif's hair has a few hints in it too - I can't find the exact source now (maybe someone can help with that?). Anyway, I've read that cutting off one's hair was seen as a sign of adultery then and that it's questioned just how Loki was able to get so close to Sif that he cut off all her hair.
So, basically, I think there is some quite strong hints in the myths themselves that Loki and Sif had a relationship and going off the Lokesanna quotes, that it was more than just a one night stand.
As for the comics, I am not very familiar with them, but there's been some interesting things on tumblr about them, suggesting there may be a few Sif/Loki hints there too. There is the latest kid Loki who definitely seems to have a crush on Sif (eg, in these comics part 1 and 2) and the past Loki who seems to covert Sif too, especially in the Loki comics (source).
There's a Thor film comic where Sif chooses to follow Loki over Thor (mentioned here and here, though no actual pictures I'm afraid - maybe someone knows where to find this comic?). Oh and then the immense Sif/Loki shippiness in the Burger King Thor comic - totally endorsed by Marvel! Does anyone know where I can read the rest of this? I think there's 4 parts, and this is only part 1. Of course, these are all quite small hints (and not the best of evidence!), but fun to mention I think all the same.
Of course, I'm happy to ship film Sif/Loki anyway, based on their awesome chemistry alone, but I finding it quite interesting how the myths are backing them up somewhat. Also, it's quite fun to compile all this little tidbits of evidence. Just to show that Loki/Sif are far from a crack pairing! Oh and please let me know if I've missed anything!
Now, we just need to see some actual Sif/Loki revelations in Thor 2 and 3!