Sudan really is very friendly!

Teaching in a university. Very much make what you can of it. Start English clubs, start lessons to fill the knowledge gap of basic English you are likely to find. I ended up attempting to teach Hamlet as it was on their syllabus and they were struggling- not the best idea!
I was alone in town for almost half my stay. This was tough, but my colleagues and many people I met were very friendly and welcoming. It was easy to find extra work to keep busy and people to visit and eat with. Many volunteers are placed together and I lived with another volunteer for the other half- which was great. We really got to be part of a community.
It is hot, like really hot.
Be prepared to have everyone greet you on the street or shout "khawaja"- "foreigner" at you. They're just surprised.
Islamic culture, so long clothes for women, no alcohol (unless you know where to look for it), very different gender relations. But generally people are friendly and eager to share their culture with you rather than make you feel unwelcome.