The two women are identified "Miss A" and "Miss W" in Sweden to protect their identities.
On 11 August 2010, Assange arrived in Sweden to speak at a seminar partly arranged by "Miss A". He had met her before but he stayed at her apartment. They had sex on 14 August 2010.
At the seminar, Assange met "Miss W" and they had sex on 17 August 2010.
On 19 August 2010 the two women (who are friends) discovered that both of them had had sex with Assange. Up to this point neither had suggested that the sex was anything other than consensual, but that day they decided to contact a journalist and complain about their sexual encounters with Assange. The journalist insisted they contact the police and the two women went to the police together. They both say that what started as consensual sex became non-consensual, which is rape in Swedish law. The two women were interviewed together by police and this allowed contamination of their evidence.
On 20 August 2010 a warrant was issued for Assange's arrest. On 21 August it was withdrawn by Stockholm's Chief Prosecutor. On 30 August, Assange was interviewed by police.
On 1 September 2010 a different prosecutor announced that she was reopening the investigation. This is not a normal procedure in Sweden. Furthermore, the prosecutor identified Assange to the press, which is against Swedish law. On 2 September she re-interviewed the complainants, but she did did not interview Assange, which is required within a week - she said this was not done because of a police officer being sick.
On 5 September 2010 a journalist reported that the two women did not want to proceed.
On 27 September 2010 Assange left Sweden with the agreement of the authorities.
On 18 November 2010 a court approved a request to detain Assange for questioning. On 20 November an international arrest warrant was issued. It was possible to interview Assange in the UK, as there is a mutual legal assistance agreement, but the prosecutor went for the arrest warrant instead.
That's where we stand at present. Assange has not been charged with a crime as yet.
Frankly it looks like a case where two women discovered that they were both having sex with Assange and decided (together) to come up with a way to get back at him - there's no way to prove that sex becomes non-consenual while it is in progress. It's a classic "he said, she said" situation. It's strange that both women claimed the same thing happened, but not until they had discovered they were sharing his favors.
It appears that the prosector has an agenda, but I have no idea why.