I've been reading various conflicting information about visiting Tskhinvali. Are there buses or marshrutkas leaving Gori going into Tskhinvali? Would I have to get permission from the Ministry of Foreign Affairs of South Ossetia to visit? I would also like to cross back into Georgia, is this possible? I plan to go in May 2013; the information on the web that I have found has no dates so I don't know if anyone has any updates. Thanks.
Sorry all links but one is in Russian.
As far as I can tell the official stance on the Border crossings between South Ossetia and Georgia is that there is none so officially you can't cross between Georgia and South Ossetia be it in Gori or otherwise.
The only way you can officially visit South Ossetia would be if you enter through Russia and you can cross on the only land crossing available which is Казбеги-Верхний Ларс(English version), which has been opened between Georgia and North Ossetia since 2010 and from the first link has begun working 24 hours as of this year.
P.S. This information is as of today and may change without notice tomorrow.