Very briefly, these are the main contenders:
Mac Ahlberg, using the pseudonym Bert Torn, directed a series of classy-looking films in the 70's: "The Second Coming of Eva", "Flossie", "Justine and Juliette" aka "Swedish Minx", "Bel Ami" and "Molly".
Torgny Wickman directed several famous and entertaining educational films, such as "The Language of Love" (Robert de Niro takes Cybil Shepherd to see one in "Taxi Driver"), but also plot-driven films like "Countrylife".
Paul Gerber, an American, did two interesting films, "Ceremony" and "My Teenage Daughter". Especially the latter is a bit of a legend, and rightly so.
Another American, Joe Sarno, made a bunch of films in Sweden during the 60's and 70's, well worth seeking out.
A Romanian, Andrei Feher, lived in Sweden for a while and made films. He eventually shot more and more in France, but retained his Swedish production company. Feher mostly worked with French performers, sometimes giving them Swedish pseudonyms (i.e. Dominique St Claire became "Barbi Andersson").
Bo A Vibenius made the most notorious one, "Thriller - A Cruel Picture" aka "They Call Her One-Eye", and also directed the little-seen "Breaking Point". Weird movies, representative of the sick 70's.
As for performers, Marie Fors? aka Maria Lynn, stands out. She only did full-on hardcore in magazines (at least one), but reportedly had real sex during some of her scenes (as can be seen in Sarno's "Butterflies").
Marie Ekorre, Christina Lindberg, Marie Liljedahl, Inger Sundh, Leena Skoog and Solveig Andersson were the famous names, but none of them did hardcore. Anita Ericsson did, and so did Jack and Kim Frank, an energetic live show couple of the times. "Leena" (not Skoog) was big during the late 70's, as was Oili Virta. Both these models were of Finnish descent.
The classical "Schweden-Film" era started big-time around 1965 and lasted until ca 1980. Even during its heyday, performers were hard to find and many of the Swedish classics are international co-productions with international casts (Harry Reems pops up in a couple, as does Eric Edwards, Kim Pope, Gilda Arancio, Brigitte Maier and a bunch of Danes such as Anne Magle, Bie Warburg and Lisbeth Olsen.)
There is a good internet resource:
www.klubbsuper8video.com They have reissued many of these films (they also have some none-sex cult titles) and are having a grand clearance sale at the moment (VHS only, they will move into DVD soon). The site is only in Swedish, but send them a message, they speak good English. The films themselves are not subtitled, but some of them are actually made in English.
Sadly(?), my knowledge regarding current Swedish adult cinema is rather limited. Anyone up for the challenge?