Some of the easiest species to get to flower are andersonii, livida and bisquamata. They will flower soon after planting and will keep flowering over long periods of time. When the flowering slows down, start a new colony with a small piece of the old one.
Other interesting species that will flower given the opportunity are U dichotoma, U. flaccida (large yellow flowers, an 18 inch branching inflorescence), U welwitschii (tightly twining inflorescence with many pink, yellow and white flowers), U. tridentata (medium size pink flowers with a yellow palate.
Of course some of the more unusual species may be hard to find.
You may also want to try the easy Genlisea species G. hispidula and violacea.