Photo Equipment: If you have a camera with APS make sure to bring loads of rolls of films from back home, as you won't be able to buy it in neither Sengerema or Mwanza. You have to go to either Moshi, Arusha, Dar or Kampala (!) to buy them and they are often more expensive than if you had bought them back home. Also, I wouldn't recommend developing APS-photoes down there as they simply don't know them. You can get ordinary rolls of film developed in Mwanza and they are perfectly fine, but don't risk it if you have APS
Luggage and bags: Bring a mobile phone from back home and simply change the SIM card in Mwanza and buy VodaCOm Vouchers when you need to call. Communication is really important down there, and it is crucial you have a way of getting into contact with people if you need help. A lot of Tanzanians also have a mobile and it just makes life so much easier if you have one. Some times the network is down in Sengerema, but it usually doen't last more than a day or two.
Clothing/Shoes/Weather Gear: Bring rain clothes as it DOES NOT exist in etiher Sengerema or Mwanza! Sure, you will be able to buy umrellas, but that just doesn't cut it in the rainy season. You will look like a drowned mouse if you don't have rain clothes.