At any rate, below is an incomplete list of abbreviation I toss around on a frequent basis; as a military man I don't really think too much about the fact that not everyone knows what these means,
UNMIS - United Nations Mission in Sudan (mandate ended 9th July 2011)
UNMISS - United Nations Mission in South Sudan (mandate started 10th July 2011)
UNISFA - United Nation Interim Stabilizing Force Abyei (the new mission in Abyei area)
UNMISS - United Nations Mission in South Sudan (mandate started 10th July 2011)
UNISFA - United Nation Interim Stabilizing Force Abyei (the new mission in Abyei area)
UNHCR - United Nations High Commissioner for Refugees
TS - Team Site
LA - Language Assistant
NM - National Monitor
SAF - Sudanese Armed Forces (the armed forces of northern Sudan)
SPLM - Sudan People's Liberation Movement
SPLA - Sudan People's Liberation Army, the military wing of SPLM (and after the CPA, the armed forces of southern Sudan)
CPA - Comprehensive Peace Agreement
NGO - Non-Government Organisation, ie an organisation which may or may not be non-profit, but is independent of any government
INGO - International NGO, not often used as most NGOs are international anyway
SSPS - South Sudan Police Service, the civilian police of southern Sudan
More to come as I can think of them.