If travelling to Uganda, dont be surprised when you are asked to pay 100 USD for single tourist visa. The raise of Ugandan single tourist visa is effective from July 1st 2015.
Many Ugandan High Commissions and Embassies too are still unaware of the visa fee changes and their respective websites continue to show the fee of 50 USD. However, visa is available upon arrival at any point of entry to the country.
Dont forget, in se your travel plans include visiting Kenya, new visa policy requires to obtain it online prior arrival.
Read more about Kenyan Visa