We thought the Sea View Lodge in Jambiani was absolutely wonderful. It's a tiny little place, with just four rooms at the moment, though the owner did mention that they'd like to add another one or two rooms at some point.
Each room is right on the beach, just steps from the sea when the tide is in and each has its own pair of sun loungers with a coconut thatch sun shade. Our room was lovely, equipped with a clean and comfortable double bed with mosquito net, space to store clothes, a fan to keep it cool (when the electricity was working that is - it is a bit erratic in Zanzibar!) and an en-suite wet room style shower room with WC. What more do you need? We prefer small locally run hotels and lodgings, so to us, it was blissfully perfect. If you're more at home in a generic Hilton type hotel it might not be your thing, but if you like clean but rustic local places the chances are you'll love it here. The owners are wonderful - nothing was too much trouble and we felt they really looked after us and wanted us to enjoy our stay.
The room price included a great breakfast of fresh fruit, juice, eggs and tea or coffee and you can sit and watch life go by on the beach as you start the day. They will also cook lunch and evening meals, but we found it best to choose something early in the day and check with them to see if they could get the necessary ingredients (Jambiani is just a small village, so ingredients are obviously restricted to what's available at the time) - we had a couple of really good meals here and it was no problem to apply common sense and pre-plan a bit. Alternatively, there is also an excellent little restaurant just a few steps away and other places an easy stroll up the beach.
The local village runs the length of the beach behind the hotels and restaurants and is easy to get to - we really enjoyed strolling through and found everyone to be wonderfully welcoming and friendly.
Jambiani beach is great... the tide goes in and out so you need to plan the swims a little bit, but when the tide is out it's alive with local ladies tending their seaweed farms, so there's always plenty to see and we much preferred it to the 'resort' atmosphere that we found in the north at Nungwi where the tide is pretty much always in. The sea temperature was amazing, just like getting into a warm bath.
It was a slice of paradise.