The Independent  explains the key actors, and reasons for the violence:

The short-term cause of the violence is over the proposed visit by the Kabaka to Kayunga district, within the Kingdom of Buganda, on Saturday to preside over a youth celebration. In reaction to the upcoming visit the Banyala, a tribe who have their own kingdom claims in Kayunga, demonstrated against the Kabaka. The unrest led to government officials advising the Kabaka against visiting the region as the police could not guarantee his safety. On September 7th, Buganda youth tried to begin setting up stalls in Kayunga town ahead of the visit, but were on by anti-riot police. This scenario then repeated itself on the 9th. Then yesterday, Thursday, the Katikkaro-- the 'Prime Minister' of the Mengo Parliament- tried to make an advance visit to Kayunga, but was blocked at the district border by a high-level police delegation. As word spread of the police action Buganda youth began mobilising rioters beginning in Kisseka market. The riots then began spreading throughout Kampala city and finally to most of the districts in the central region of Uganda. 

In its editorial the Daily Monitor  urges President Museveni to allow the Kabaka's visit:

Uganda is a multi-ethnic society where people of different tribes have for decades lived peacefully irrespective of their tribal differences. [...] the Kabaka since his enthronement in 1993, has on several occasions visited the area without any hullabaloo. Why is he being stopped now? It is important to note that it is just a small group of Banyala who are backing the anti-Kabaka drive because family members of Capt. Kimeze on Wednesday held a press conference in Kampala and denounced the actions of their brother. 

Twitter, blogs and Facebook have played an active role in providing witness as people on the streets report their accounts. Solomon King, a blogger and web developer, has been active updating the rest of the world with posts and photos of the riots on his blog Rogue King . King also tells us that there is limited coverage on local television on the riots. Tumwijuke Mutambuka who blogs at the Ugandan Insomniac has a number of posts covering the riots. She wonders why there is little coverage on the riots.

If ever you needed proof that the broadcast media in Uganda is out of touch with reality, go on; turn on your radio. 

With several radio stations shut down Mutambuka wonders at the incompetency of radio broadcast in Kampala :

Where were the spot reports? What is radio for if not for immediate news immediately? Where was the citizen talk-back? Why no discussion of the hooliganism of many of the protesters? Where are the rolling interviews with the Buganda Kingdom, the police and the government? Where were the call-ins from Masaka town, Nyendo, Kayunga and Mukono where the rioting was taking place? Why no debate on media freedom? Why no discussion on why the Broadcasting Council exists? 

Blogspirit , an aggregate of Ugandan bloggers has a list of blog posts on the riots. 

Musician, Kirk Franklin, who is in Kampala for a concert that has now been cancelled, v-blogs about his experience during yesterday's riots. Money quote: "Those kind of things happen in Africa." 

If you are on twitter search for the following hashtags on frequent updates on the situation on the ground: #kampala, #ugandawitness. Also on twitter follow @solomonking, @Uginsomniac , @dailymonitor,  @UgandaTalks, @mugumya, @camaraafrica and  @appfrica for frequent updates.  We learn from  Jonathan Gosier of App Africa that Uganda Telecom is offering free twitter usage to its subscribers.  

Witnesses can, and are using, Ushahidi's crowd sourcing application for collecting crisis information to report incidences as they happen on Uganda Witness where you can see where violence has broken out, looting, injuries and death among other things.  

Media reports indicate that renowned reporter Kalundi SSerumaga was kidnapped Friday night in an unmarked car. 

According to the Monitor: SSerumaga was kidnapped by unidentified men as he left WBS TV studios in the heart of Kampala after a live talk show. [...]

At a press conference in Kampala, Police General Major General Kale Kaihura announced that the riots had resulted in the death of 14 people, and 82 injured. He also reported that 550 people had been arrested. While he said that his force was still arresting others, he asked his officers not to fire live ammunition nor use excessive force.

 Keep checking back for more information, we will report news as we hear it.