For Acholi, I found this
, which has links to four zip files. Of these, I think the last two would be the most useful: "The Essentials of Acholi" (this may be the best starting point) and "US Peace Corps Acholi Resources."
For Alur, I found this
blog. I haven't really looked at it yet, but I thought I'd share it anyway in case it turned out to be useful.
Finally, for Lango, I just found this YouTube video. It's about a project to make Lango kids literate in their own language. There are subtitles throughout the video. A lot of the time, the people in the video are just talking in English, but then there are also many times where they are speaking Lango instead, and there are a few points where you can hear isolated words as well, so hopefully this should be useful at least for learning those: http://www.youtube.com/watch?v=YJp1vG2Tk80