East Africa Tourist Visa
Since the 1st January 2014 (or slightly thereafter), you can get a single multi-entry tourist visa for 90 days that covers Kenya, Uganda and Rwanda. I got mine at the Kenyan High Commission in Dar Es Salaam for 165,000 TZS = 100 USD.
Take along your passport, a passport photo and a letter describing why you are looking for this visa and your done within an hour.
For my route Tanzania -> Kenya -> Ethopia -> Kenya -> Uganda -> Rwanda it should save me a few shekels compared to getting a visa at the border.